An Attempt to Explain High Definition Audio

dante01

Distinguished Member
An Attempt to Explain High Definition Audio & Some Other Stuff


High Definition Audio


Blu-Ray brings with it new high definition sound formats to match its high quality pictures and video.

Sound can be stored on a disc in a number of ways:

• Lossless Uncompressed (no data lost),
• Lossless Compressed (smaller storage space needed, but no data is lost),
• Compressed lossy (some data is lost).

Compression formats that lose data (“lossy” compression) use careful algorithms to throw away data that you are supposed to be unable to hear. DVD's use these types of compression formats as space restrictions and don't usually utilise lossless audio as the video information takes up the majority of the available free space. DVDs do allow for stereo PCM, and this is especially apparent on classical music DVDs, albeit nowhere else. Stereo LPCM is one of the mandatory audio formats that all DVD players and processors must support (unlike dts). The problem is that DVD doesnt support lossless surround sound.

With Blu-Ray, discs space isn't as much an issue as it is with DVD. With 25GB per layer, multiple layer support, and dual-layer discs being the norm, the Blu-Ray disc has plenty of space to store lossless formats.

DVDs can deliver data at up to 10.08 Mbps (megabits per second) and only approximately 1.5Mbps of this is used for audio (that means all audio streams; 5.1 soundtrack, 2 channel soundtrack, director's commentary, etc.). According to the Blu-ray Disc specification, Blu-ray 1x speed is defined as 36Mbps (data) and 1.5x 54.0Mbps (video/audio). Blu-ray has the potential for much higher speeds, the only limiting factor for Blu-ray is the capacity of the hardware. The Blu-ray Disc Association (BDA) plans to raise the speed to 8x (288Mbps) or more in the future, but the current maximum video is limited to 40Mbps and audio is limited to 27.648Mbps.

Audio streams can be sent to an AV receiver/amplifier as bitstream (encoded digital data) or LPCM (essentially raw digital data.) Bitstreamed audio from a DVD or Blu-Ray disc needs to be decoded. This can sometimes be done by the player itself and output as LPCM to the amplifier/receiver. If a player lacks the inbuilt ability to decode the data, bitstreamed data can be sent for a suitably equipped AV receiver/amplifier/processor to do the decoding. Regardless of which method is used, there is no difference in quality between LPCM and lossless bitstreamed formats like Dolby TrueHD and DTS-HD Master Audio.

Along with the lossless Dolby TrueHD and DTS-HD Master Audio formats, Blu-Ray offers Dolby Digital Plus and DTS-HD High Resolution audio. While being a “lossy” formats, these two new standards offer benefits that Dolby Digital and DTS from DVD discs can't such as higher sample rates. Like Dolby TrueHD and DTS-HD Master Audio, they also offer support for 7.1 channels of audio, where DVD's can only support up to 6.1 channels.

Dolby DTS-HD Master Audio has a “core” DTS soundtrack that older receivers can lock into (fall back on) as they do with Dolby Digital and DTS soundtracks from DVDs. Like all “lossy” compression systems, the less compression, the better. With the extra space on Blu-Ray and HD DVD discs, higher compression rates aren't as necessary for the DTS “core” soundtrack, meaning better quality audio. For example, Dolby Digital 5.1 on a DVD will use a sample rate of either 384kbs or 448kbs. Blu-Ray discs will carry the same Dolby Digital 5.1 soundtrack at 640kbs. The “core” DTS soundtrack on a Blu-Ray disc is often delivered at an even higher bit rate. The Dolby TrueHD stream is actually two streams: one MLP (Meridian Lossless Packing), also known as Packed PCM and one standard Dolby Digital. TrueHD track are required to contain a standard Dolby Digital AC-3 track for compatibility with players that don't support TrueHD.



What audio codecs will a Blu-ray player support?

Dolby Digital (DD):
• MANDATORY support on BD players
• Lossy, non HD format commonly used on DVDs
• Supports up to 6 channels of discrete sound
• Sample rates: 32, 44.1, 48 kHz
• Bit Depth: 16, 20 bit
• Constant bit rate of up to 640 kbps

The audio format familiar from DVD, Dolby Digital (sometimes known as AC-3) is one of the base standards of Blu-ray. It works basically the same way that it worked on DVD in configurations from 1.0 to 5.1, though it does offer a higher maximum bit rate of 640 kb/s (which is considered audibly indistinguishable from Dolby Digital Plus at the same rate). 



Digital Theater System(s) (DTS):
• MANDATORY support on BD players
• Lossy non HD format commonly used on DVDs
• Supports up to 6 channels of discrete sound (DTS Digital Discrete up to 7 channels)
• Sample rates: 48 and 96 kHz
• Bit Depth: 16, 20, 24 bit
• Constant bit rate of up to 1.5 Mbit/s

Digital Theater System(s), also previously known as 'DTS Encore', is a holdover from standard definition DVD. DTS is an alternative and competing format to Dolby Digital. The basic difference between the two formats is the method of compression. The use of DTS is optional on DVDs. Blu-ray more ably supports the codec at a higher bit rate that used for DVD. With the extra space and bandwidth afforded by Blu-ray, DTS audio tracks can be encoded at data rates greater than 1.5 Mbit/s. DTS soundtracks found on Blu-ray discs usually have a higher bit rate than those normally found on a DVD.



Dolby Digital Plus (DD+):
• OPTIONAL support on BD players
• Compressed extension of Dolby Digital
• Supports up to 8 channels of discrete sound
• Sample rates: 48 or 96 kHz
• Bit Depth: 16, 20, 24 bit
• Constant bit rate of up to 6 Mbit/s


DD+ is a lossy format that uses a more efficient compression technique at data rates from 96Kbps to 6 Mbps, resulting in better sound quality. It can also support movie soundtracks with up to 7.1 discrete channels of sound. On Blu-ray, DD+ is encoded as an extension to a "core" Dolby Digital AC-3 track. The DD+ extension bitstream is used on players that support it by replacing the rear channels in the 5.1 setup with higher fidelity versions, along with providing a possible channel extension to 6.1 or 7.1. The complete audio track is allowed a combined bitrate of 1.7 Mbit/s: 640 kbit/s for the AC-3 5.1 core, and 1 Mbit/s for the DD+ extension. During playback, both the core and extension bitstreams contribute to the final audio-output, according to rules embedded in the bitstream metadata.



DTS-HD High Resolution:
• OPTIONAL support on BD players
• Compressed extension of DTS
• Supports up to 8 channels of discrete sound.
• Sample rates: 48 or 96 kHz
• Bit Depth: 16, 20, 24 bit
• Constant bit rate of up to 6 Mbit/s

Similar to Dolby Digital Plus, DTS-HD HR is a lossy format that offers enhancements over standard DTS with higher bit rates and better compression. It delivers up to 7.1 channels of sound at frequencies from 48kHZ up to 96 kHz and 24 bit depth resolution. DTS-HD HR is selected as an optional surround sound format for Blu-ray with constant bit rates up to 6.0 Mbit/s. It is an alternative for DTS-HD Master Audio where disc space may not allow it. DTS-HD HR is also encoded as an extension to a "core" DTS track. The DTS “Core + Extension” structure contains data for a 5.1-channel system, operating at 44.1 or 48kHz, with a bit rate of 1.5Mbps (mega-bits per second). . If you have an older DTS-capable receiver, it will “ignore” any extensions and just decode the "core". The same “Core + Extension” structure is utilised within DTS-HD MA.


Linear PCM (LPCM):
• MANDATORY support on BD players
• Lossless encoding
• Supports up to 8 channels of discrete audio
• Sample rates: 48, 96, 192 kHz
• Bit Depth: 16, 20, 24 bit
• Constant bit rate of up to 27.7 Mbit/s

A PCM track is an exact replication of the studio master, encoded on disc without compression. The benefit to this is that it maintains the purity of the source without any loss of fidelity that may come from compression. The downside is that an uncompressed audio track takes up a tremendous amount of disc space, which may (especially on single-layer BD25 discs) negatively affect the video quality of the movie. While the Blu-ray format is capable of utilising PCM audio up to 24-bit resolution, studios may choose to encode at 16-bit resolution instead, depending on the bit depth of the original source or concerns about conserving bandwidth (downsampling a 24-bit master to 16 bits is technically not the same thing as compression). 



Dolby TrueHD:
• OPTIONAL support on BD players
• Compressed Lossless encoding
• Supports up to 8 channels of discrete audio
• Sample rates: 48, 96, 192 kHz
• Bit Depth: 16, 20, 24 bit
• Constant bit rate of up to 18.4 Mbit/s


Dolby TrueHD is a "lossless" compression codec. It is compressed to take up less disc space than a PCM track, but once decoded it is bit-for-bit identical to the studio master at either 16-bit or 24-bit resolution (at the discretion of the studio) and a bit rate up to a maximum of 18.4 Mbps.



DTS-HD Master Audio:
• OPTIONAL support on BD players
• Lossless encoding
• Supports up to 8 channels of discrete audio
• Sample rates: 48, 96,192 kHz
• Bit Depth: 16, 20, 24 bit
• Constant bit rate of up to 24.5 Mbit/s

DTS-HD MA (previously known as DTS++) is a lossless audio codec similar to Dolby TrueHD. Like Dolby TrueHD, a disc encoded with DTS-HD MA delivers ALL of the information from the original master recording — bit-for-bit. The difference between the two is that DTS-HD MA uses a core+extension configuration (just like DTS-HD HR). A DTS-HD MA track takes up more disc space than a TrueHD track, but does not require a secondary standard track for backwards compatibility. Since both DTS-HD MA and TrueHD are lossless, they are both 100% identical in quality to the studio master, and hence identical in quality to each other (lossless 24-bit/192 kHz).


The three lossless audio formats associated with Blu-ray players' high-resolution audio soundtracks are Dolby TrueHD, DTS-HD MA and PCM. These formats will all convey 8 discrete channels (7.1) of "lossless" audio that exactly duplicate the original studio masters.


Blu-ray players and recorders will have to support playback of the mandatory codecs, it will still be up to the movie studios to decide which audio codec(s) they use for their releases, but Blu-Ray titles must use one of the mandatory schemes for the primary soundtrack. A secondary audiotrack, if present, may use any of the mandatory or optional codecs along with the mandatory primary soundtrack.



Bits, Rates and Frequencies


Sampling Rate or Frequency Rate is defined as the number of times samples are taken per second to convert an analog signal to digital. A higher sampling rate allows for higher frequencies to be represented. The sampling frequency also impacts fidelity. The sampling frequency is essentially the number of times the sound event is quantized within a given time period (e.g., 96kHz equates to 96,000 samples per second). Sampling frequencies are specified in KiloHertz (KHz). CD-quality sound requires 16-bit words sampled at 44.1 KHz. Essentially this means 44,100 16-bit words (705,600 bits) are used to digitally describe each second of sound on a compact disc.

Bit Depth (Word Length) is the number of bits (8, 16, 24 etc,) used to represent the analog audio signal each time it is sampled in the analog-to-digital conversion (ADC) process. A higher bit number allows a more accurate representation of the amplitude of an audio signal, resulting in better dynamic range. Generally a larger Bit Depth equals higher fidelity. 24-bit is generally considered the current practical limit as this Bit Depth allows a signal-to-noise ratio exceeding that of most analog circuitry, which by necessity must be used at least twice in the recording/playback chain (ADC and DAC).

Bit Rate or Data Rate refers to the number of bits used per unit of playback time to represent a continuous medium such as audio or video. It is the number of bits-per-second that can be processed, calculated by multiplying (sampling rate) x (sample size) x (number of channels).



Digital Audio and LPCM


Digital audio begins when an analogue audio signal is first sampled, and then converted into binary signals. An analog signal is converted to a digital signal at a given sampling rate and bit resolution; it may contain multiple channels (2 channels for stereo or more for surround sound). Generally speaking: the higher the sampling rate and bit resolution the more fidelity, as well as increase the amount of digital data.

A digital audio signal starts its life with an analog-to-digital converter (ADC) that converts an analog signal to a digital signal. The ADC runs at a sampling rate and converts at a known bit resolution.

After being sampled with the ADC, the digital signal may then be altered in a process which is called digital signal processing (DSP) where it may be filtered or have effects applied. The digital audio signal may then be stored or transmitted to another digital device.

Digital audio needs to be converted back to an analog signal with a digital-to-analog converter (DAC). Like ADCs, DACs run at a specific sampling rate and bit resolution but through the processes of oversampling, upsampling, and downsampling, this sampling rate may differ to the initial sampling rate. All devices capable of accepting incoming digital audio and outputting analogue audio possess a DAC.

For audio, BD-ROM (Blu-Ray) players are required to support Dolby Digital, DTS, and linear PCM. Players may optionally support Dolby Digital Plus and DTS-HD High Resolution Audio, as well as lossless formats Dolby TrueHD, DTS-HD Master Audio (MA) and Linear PCM (Linear Pulse-Code Modulation). Blu-Ray titles must use one of the mandatory schemes for the primary soundtrack. A secondary audiotrack, if present, may use any of the mandatory or optional codecs.

Bitstream is usually the output of an audio or video encoder. The elementary stream contains only one kind of data, e.g. audio, video or closed caption. An elementary stream is often referred to as "elementary", "data", "audio", or "video" bitstreams or streams. The format of the elementary stream depends upon the codec or the type of data carried in the stream itself. The Source device does not decode the signal and the device receiving the bitstream must be capable of decoding it. Think of bitstreaming as passing data through untouched. For example, if your Blu Ray player cannot decode Dolby TrueHD / DTS-HD Master Audio but your AV receiver can, you need to set the digital output of your player to "Bitstream". In other words, the encoded audio will be streamed to the AV receiver / amp in order for it to do the decoding.

Linear pulse code modulation (LPCM) is a method of encoding audio information digitally. The term also refers collectively to formats using this method of encoding. LPCM can be included on the disc itself or the player can derive LPCM from other digital tracks if it posses the ability to decode them. The player then transports the raw LPCM or decoded as LPCM audio through the player's digital connections to other devices such as an AV receiver. For example, if your Blu Ray player can decode Dolby TrueHD / DTS-HD Master Audio but your AV receiver can't, you need to set the digital output of your player to "LPCM" or "PCM". In other words, the encoded audio will be decoded by the player in order for it to be streamed to the AV receiver / amp as LPCM.

LPCM is used for the lossless encoding of audio data in the compact disc Red Book standard and has been defined as a part of the DVD and Blu-ray standards as well as the digital audio standard frequently called AES/EBU. Stereo LPCM is one of the mandatory audio formats that all DVD players and processors must support.

The term PCM is often used to describe data encoded as LPCM. PCM is a digital representation of an analog signal where the magnitude of the signal is sampled at regular intervals and then mapped (quantized) into binary code. The quantization is necessary because CPUs are used to implement DSP (Digital Signal Processing). Computers can only process finite quantities at any one time. Signals need to be mapped to fit a finite resolution, so that they can be stored in a CPUs registers and memory while the DSP takes place. PCM ís basically a stream of "1s" and "0s" (bits, "ons" and "offs") that precisely describe the frequencies and relative loudness (amplitude) of a music signal. No data is discarded to conserve bandwidth or reduce file size. The "1s" and "0s" are used by the DAC to reconstruct the original audio in order that the original audio may then be amplified and output as analogue by your AV amp or receiver.

Quantization is the fundamental element that distinguishes lossy data compression from lossless data compression, and the use of quantization is nearly always motivated by the need to reduce the amount of data needed to represent a signal.

Aimost all new BD players can decode the Dolby TrueHD / DTS-HD MA lossless audio and send it to your receiver as a multichannel LPCM stream. Just about any modern AV receiver can decode LPCM even if unable to decode Dolby TrueHD / DTS-HD Master Audio. The LPCM audio is identical to the Dolby TrueHD / DTS-HD MA original format, so no quality is lost.



So What Do You Need?

Firstly you'll need a Blu-Ray player and some discs encoded with the new formats.

You'll also need an AV receiver/amplifier/processor. It needs to be compatible with high definition audio – either with onboard HD audio decoding abilities or the ability to accept and then decode multichannel LPCM. The format compatibility labels on the front of some units might only list Dolby TrueHD and DTS-HD Master Audio but Dolby Digital Plus and DTS-HD High Resolution audio will also be covered by these units. Some early 7.1 receivers and amplifiers may show no external signs of being compatible with the new formats and do not posses the inbuilt ability to decode these formats for themselves. However it is possible to send the required audio streams to them as LPCM from players with their own inbuilt decoders.

When you decode Dolby TrueHD / DTS-HD MA tracks, you get an identical copy of the original audio – this is why it's called "lossless." On Blu-ray discs, the Dolby TrueHD and DTS-HD MA codecs can include up to eight channels of lossless audio information, each channel with up to 24-bits resolution at a 96kHz sampling rate, commonly referred to as "24/96."

The vast majority of HD audio compatible receivers will be 8 channel, usually referred to as 7.1 (there are a few exotic HD processors (amps, receivers) that only support 5.1 LPCM over HDMI) and an increasing number of entry level 5.1 AV amps and receivers that also come with HD audio decoding abilities. The majority of Blu-Ray titles currently available only offer 5.1 DolbyTrueHD or DTS-HD Master Audio. It is acceptable to purchase 5 speakers and upgrade to 7 speakers at a later date when 7.1 channel audio on Blu-Ray discs becomes common place. Seven speakers plus a subwoofer isn't a strict requirement and you can happily use 5 speakers attached to the 7.1 AV receiver/amplifier.


Connections

In AV amps that use HDMI "Switches" (not "Repeaters"), the HDMI input is not connected to anything other than the HDMI output . This means the digital audio can only pass straight out the AV amp and into the display device (passthrough). The sound can NOT be heard via the speakers connected to the AV amp. The sound is still digital when it reaches the display device and as display devices generally only deal with analogue audio (2 channel stereo, not multichannel digital), they can not perform digital to analogue conversion on the digital audio and extract the full multichannel digital sound track that may be in the audio stream. You must connect the player to the AV amp with an additional digital audio cable, such as an optical (TOSLINK) cable (Not suitable for streaming HD audio), use multichannel analog input / output jacks (suitable for streaming HD audio, but not always a viable option), or utilise an AV amps that utilises an HDMI "Repeater".

In AV amps that use HDMI "Repeaters" (not "Switches"), the HDMI Repeater is connected to the internal electronics of the AV amp. This
means the AV amp can perform the necessary DAC and decoding to the digital signal so that it can be amplified and output to the speakers connected to the AV amp. This means no further connections are necessary from your HDMI source device to the HDMI AV amp as all data can be sent and handled by the HDMI repeater.

S/PDIF transmission aren't compatable with HD audio streaming. Due to bandwidth limitations, neither coaxial nor optical digital connections support multichannel HD audio streams. If you connect your Blu-Ray player to an AV receiver with optical or coax, the audio will "fall back" to Dolby Digital, DTS or two-channel PCM (lossless, but only two channels).

Note that you don't specifically need a receiver equiped with HDMI v1.3. First-generation HDMI provides full-bandwidth playback of Dolby DigitalPlus/Dolby TrueHD and Dts High Res Audio/dts Master Audio signals decoded to LPCM inside the player while HDMI 1.3 (version number refers to the interface on the receiver/amp and not the cable used) can handle/transport Dolby Digital, Dolby Digital Plus, Dts High Res Audio/dts Master Audio and Dolby TrueHD bitstreams (from players equipped with bitstream output capability) directly to AV receivers equipped with Dolby Digital Plus/Dolby TrueHD and Dts High Res Audio/dts Master Audio decoding.

If you lack HDMI connectivity between the player and the AV receiver or the type of HDMI interface on your AV amp is only an HDMI "Switch", you'll need a player and AV receiver with a set of multichannel analog input / output jacks. You'd need the player to perform the decoding in order for it to send the LPCM data to the AV receiver via its multi-channel analog outputs to the corresponding inputs on the AV receiver. Multichannel analog outputs give full-bandwidth playback of Dolby Digital Plus/Dolby TrueHD and Dts High Res Audio/dts Master Audio soundtracks decoded to LPCM inside the player and connected to an AV receiver equipped with multichannel analog inputs. However, most receivers do not apply DSP postprocessing to analog input signals. In these instances, a Blu-ray player that provides bass management (particularly important if you have a sub/satellite speaker system) is preferable.

It should be noted that when sending LPCM rather than the Dolby TrueHD / DTS-HD MA bitstream, the AV receiver's Dolby TrueHD / DTS-HD MA indicator will not light up. This is because the AV receiver is not decoding Dolby TrueHD / DTS-HD MA – the BD player already did the decoding. Instead, the receiver will (correctly) indicate that it is receiving a LPCM audio stream.


The Sony Playstation 3 (PS3): HD LPCM, but no bitstream

If your Blu-ray player can decode Dolby TrueHD or DTS-HD Master Audio, it's said to have onboard decoding for that format. That means the player itself converts the soundtrack to Linear PCM, which it can then be sent to a compatible receiver.

The PS3 lacks multichannel analog outputs and lacks the ability to bitstream HD audio to an external decoder, but can decode Dolby TrueHD or DTS-HD Master Audio onboard. This allows the PS3 to send the resulting multichannel Linear PCM (LPCM) stream to a suitably equipped AV amp/receiver via its HDMI interface.

You'll need to output to a device that can read multichannel Linear PCM (LPCM) at 7.1 channels via its HDMI input. If the receiver/amp cannot handle multichannel LPCM, the audio will be output at 5.1 channels instead. If you use LPCM, but output via the PS3's digital optical connection, you are limited to 2 and 5.1 channel sound. The multi-A/V-out (either component or composite video) only supports 2 channel audio.

In order to take advantage of the the lossless codecs with the PS3, you must stream multichannel Linear PCM (LPCM) via the PS3's HDMI output. To do so, go to the PS3's XMB interface:

Settings -> Video Settings

Once there, scroll down to the BD/DVD Audio Output Format (HDMI) and set the PS3 to stream Linear PCM. This will force the PS3 to decode the Dolby TrueHD / DTS-HD MA tracks onboard and send them out as lossless LPCM via the HDMI connection.

You can ensure everything is is set-up correcly by going to:

Settings -> Sound Settings

Make sure the PS3 audio is set to go out over the HDMI connection and that the necessary LPCM formats (24-bits at 96kHz) are enabled.

For more information regarding the PS3's "Audio Output Settings":
http://manuals.playstation.net/document/en/ps3/2_60/settings/audiooutput.html

http://www.youtube.com/watch?v=c5SnqnOjbZw&feature=player_embedded

New Caveat: The PS3 Goes Slim

The slim Ps3 supports Dolby TrueHD and DTS-HD Master Audio bitstream output to your receiver. The HDMI chip on previous generations of the PS3 didn't support bitstream output of the new(ish) high def codecs like Dolby TrueHD and DTS-HD MA. As such, the PS3 had to decode it internally before sending it over to your receiver via LPCM. PS3 Slim owners can bitstream the HD audio formats and have the indicators for TrueHD or DTS-HD MA light-up on their receivers.

New to the PS3 via Firmware update 3.3:
Bitstream (Direct) and Bitstream (Mix) have been added as options under Video Settings > BD Audio Output Format (Optical Digital).


Note: It should be said, as previously noted, that an AV amp/receiver with onboard HD audio decoding abilities will not indicate the resulting input as being anything other than Linear PCM i.e the receiver's Dolby TrueHD / DTS-HD MA indicator will not light up if the HD audio is being streamed as LPCM.







Related Topics:
http://www.avforums.com/forums/av-a...3908-list-older-av-receivers-accept-lpcm.html

http://www.avforums.com/forums/av-amplifiers-receivers/533629-hdmi-v1-3-a.html

http://www.avforums.com/forums/av-a...dvantages-hd-audio-board-decoding-v-lpcm.html


Additional Reading:
Application Definition Blu-Ray Disc Format
http://www.blu-raydisc.com/Assets/D...name=bdj_gem_application_definition-15496.pdf

Signal to Noise - Dolby TrueHD & DTS-HD MA vs. Uncompressed PCM
http://www.hemagazine.com/node/Dolby_TrueHD_DTS-MA_versus_Uncompressed_PCM

Bitstream versus PCM debate for high-density compact disc
http://www.meridian-audio.com/ara/bitstrea.htm

Blu-ray Audio Explained
http://www.soundadviceblog.com/?page_id=1140

The Blu-Ray Disc Association
http://www.blu-raydisc.com/en.html

Dolby TrueHD Audio Coding for Future Entertainment Formats
http://www.dolby.com/uploadedFiles/zz-_Shared_Assets/English_PDFs/Consumer/truehd-white-paper.pdf
 
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Passingbat

Distinguished Member
I think people will find this an interesting read. Issued by Yamaha and obviously refers to their recievers but covers all the HDMI formats and the difference between HDMI 'switching' amps and as they call it HDMI 'Repeater' amps.

http://www.yamaha-uk.com/pdf/hdmi guide5.pdf
 

Passingbat

Distinguished Member
Multichannel analog outputs give full-bandwidth playback of Dolby Digital Plus and Dolby TrueHD soundtracks decoded to LPCM inside the player and connected to an AV receiver equipped with multichannel analog inputs. However, some receivers do not apply DSP postprocessing to analog input signals. In these instances, a Blu-ray player that provides bass management (particularly important if you have a sub/satellite speaker system) is preferable.

To expand on this, using amps that don't provide post processing (I would have thought most of the popular amps) you need to add 10-15db to the sub channel when using the analogue ins. Some amps can provide this JUST for the analogue ins, others can't at all and some apply it globally so that you have to reduce it back to normal when playing DD and DTS via optical or coaxial. An option is to reduce all the channels apart from the sub in the player's set-up by 10-15db (if the player has that range of setting). or use a combination of settings in the player and amp.

The 10db is required anyway as the as the DTS and Dolby specs reduce the LFE channel by this ammount to prevent clipping, knowing it will be restored in the amp's processing. The extra 5db is required if the speakers are set to small in the players settings, to allow for the re-directed bass.

Edit: Of course another option is to turn the input on your sub up till it sounds right; just remember to turn it back down again for DTS/DD:D
 
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mentasm

Distinguished Member
I'd change 'lossless' to 'uncompressed', 'compressed lossless' to 'lossless' and the last one to lossy, although I'd say the first change would be the most helpful.

Does TrueHD strictly have a 'Core' element on BD? I thought it was a separate, hidden (although sometimes shown in the menus), Dolby Digital track, rather than a core element with extensions (like DTS-HD)?

I'd also take the apostrophes out of 'DVDs' and add hyphens to DTS-HD, but that's just me being a spelling/grammar Nazi! :D
 

dante01

Distinguished Member
I'd change 'lossless' to 'uncompressed', 'compressed lossless' to 'lossless' and the last one to lossy, although I'd say the first change would be the most helpful.

That would make it technically incorrect.

Does TrueHD strictly have a 'Core' element on BD? I thought it was a separate, hidden (although sometimes shown in the menus), Dolby Digital track, rather than a core element with extensions (like DTS-HD)?

DTS-HD Master tracks also possess the lower-quality "core" audio tracks that are compatible with older equipment. The use of the word "core" is technically correct. ;)
 

mentasm

Distinguished Member
That would make it technically incorrect.
Fair enough, but would you mind explaining why? PCM is always referred to as uncompressed by studios, so I'm curious about the specifics of the definitions.

DTS-HD Master tracks also possess the lower-quality "core" audio tracks that are compatible with older equipment. The use of the word "core" is technically correct. ;)
I know the term 'core' is used with DTS-HD tracks, but I'd never heard it used in conjunction with TrueHD. I always thought DTS-HD was based on Core+Extensions, whereas TrueHD is two separate tracks, albeit with one of them 'hidden'. Again, I bow to superior knowledge.
 

dante01

Distinguished Member
Fair enough, but would you mind explaining why? PCM is always referred to as uncompressed by studios, so I'm curious about the specifics of the definitions.


I know the term 'core' is used with DTS-HD tracks, but I'd never heard it used in conjunction with TrueHD. I always thought DTS-HD was based on Core+Extensions, whereas TrueHD is two separate tracks, albeit with one of them 'hidden'. Again, I bow to superior knowledge.

Lossless doesn't necessarily mean uncompressed and can't see why it makes a difference as long as a differentiation is made between lossless with and without compression? ;) Is the way I put it not clear?

Anyway, I've changed it to:
• Lossless Uncompressed (no data lost),
• Lossless Compressed (smaller storage space needed, but no data is lost),
• Compressed lossy (some data is lost).


You may be correct about DTS-HD and TrueHD and bow to your superior knowledge ;) Feel free to rewrite the incorrect passage and I'll amend the original (with credits).
 
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MarkusThatch

Distinguished Member
What's the story with disks that say pcm and have dts hd master audio logo too? Example is starship troopers uk disc whereas say the departed just says dts master audio no mention of pcm.
 

dante01

Distinguished Member
What's the story with disks that say pcm and have dts hd master audio logo too? Example is starship troopers uk disc whereas say the departed just says dts master audio no mention of pcm.

Linear PCM (LPCM) is mandatory for Blu-ray whereas Dolby TrueHD and DTS-HD Master Audio are optional. A PCM track is an exact replication of the studio master, encoded on disc without compression. While the Blu-ray format is capable of utilising PCM audio up to 24-bit resolution, studios may choose to encode at 16-bit resolution instead, depending on the bit depth of the original source or concerns about conserving bandwidth (downsampling a 24-bit master to 16 bits is technically not the same thing as compression). Also note, all Blu-ray disc players are required to support PCM audio.

Whether stated or not, all Blu-ray discs include PCM audio.

Linear PCM isn't, strictly speaking, a codec, because it is simply a way of representing the digital audio data in its original form, without compression. Blu-ray discs often contain an LPCM audio track of up to 7.1 channels. The added two channels, in addition to the usual 5.1, represent extra channels for speakers positioned in the very rear of the listening room.

I'd hazard that PCM isn't always listed on the BD packaging because it isn't a codec and because it is mandatory, therefore always expected (required) to be there regardless?
 
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mentasm

Distinguished Member
As far as I'm aware, The Departed doesn't have a PCM track in the UK (It's Master Audio). Starship Troopers (the original one) only has PCM, unless they've reissued it recently. Are you sure it's not just a standard DTS logo (the foreign dubs are DTS and there's an English Dolby Digital track as well)? In my experience PCM is always listed when in is available, or at least it is on all of the discs I own.
 

dante01

Distinguished Member
As far as I'm aware, The Departed doesn't have a PCM track in the UK (It's Master Audio). Starship Troopers (the original one) only has PCM, unless they've reissued it recently. Are you sure it's not just a standard DTS logo (the foreign dubs are DTS and there's an English Dolby Digital track as well)? In my experience PCM is always listed when in is available, or at least it is on all of the discs I own.


PCM is mandatory on Blu-Ray as are Dolby Digital and DTS. Master Audio is optional, while you can omit Master Audio, you may not omit PCM, Dolby Digital or DTS. PCM is the mandatory lossless audio format awarded to Blu-ray. Formats such as TrueHD, Dolby Digital Plus and Master Audio may be totally omitted and are optional.
 
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MarkusThatch

Distinguished Member
As far as I'm aware, The Departed doesn't have a PCM track in the UK (It's Master Audio). Starship Troopers (the original one) only has PCM, unless they've reissued it recently. Are you sure it's not just a standard DTS logo (the foreign dubs are DTS and there's an English Dolby Digital track as well)? In my experience PCM is always listed when in is available, or at least it is on all of the discs I own.

I'm pretty sure starship troopers has a dts master audio logo (the uk version).

Edit: it's the same on the back of the crimson tide bluray.
 

mentasm

Distinguished Member
PCM is mandatory on Blu-Ray as are Dolby Digital and DTS. Master Audio is optional, while you can omit Master Audio, you may not omit PCM, Dolby Digital or DTS. PCM is the mandatory lossless audio format awarded to Blu-ray. Formats such as TrueHD, Dolby Digital Plus and Master Audio may be totally omitted and are optional.

I think you're a bit confused. It's mandatory that players support PCM, but it's not mandatory to use it on all discs (that seems to be what you're saying, apologies if I'm misinterpreting your statement). It's evident that most discs do not have PCM soundtracks because they take up loads of space. Discs have to include one, but not all, of the mandatory codecs (PCM, DD or DTS). Putting aside optional codecs like TrueHD and DTS-HD, you'll find that discs with PCM soundtracks usually include Dolby Digital soundtracks for legacy support, as you're limited to two-channel PCM over coaxial/optical (the Kill Bill discs spring to mind).

As for Starship Troopers, I own the UK disc and I'm pretty sure that it only has a PCM soundtrack, but I'll check tonight. It's most probably a just a sleeve error. I don't own the UK edition of The Departed, but reviews state that it's DTS-HD while other regions are PCM (I have the US disc).
 

dante01

Distinguished Member
I think you're a bit confused.

No, I'm not confused at all.

Movies (dialog, music and sound effects) are recorded, mixed, edited and everything else in PCM. This multi channel PCM master track can be put directly onto Blu-ray disks with up to a maximum of eight channels (7.1) and in either 16 bit or 24bit format and at 48khz or 96khz sampling rates. All the other audio formats use this PCM master track and compress it, using lossy or lossless algorithms so that it takes less room on the disk.

PCM has to be present! It isn't a codec and it isn't an audio track, it is the raw data required to construct said audio! It is a data format and not an audio format wrapped in a carrier like AC-3 is. It isn't licensed and doesn't require you display a badge or logo in recognition of its licensing like Dolby insists upon.

PCM is mandatory on Blu-Ray discs as are Dolby Digital and DTS. Formats such as TrueHD, Dolby Digital Plus and Master Audio may be totally omitted and are optional.
 
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MarkusThatch

Distinguished Member
As for Starship Troopers, I own the UK disc and I'm pretty sure that it only has a PCM soundtrack, but I'll check tonight. It's most probably a just a sleeve error. I don't own the UK edition of The Departed, but reviews state that it's DTS-HD while other regions are PCM (I have the US disc).

Please do, it must be a recurring error then as it says the same on the reverse of crimson tide and I think also on the reverse of robocop. The logo is pretty clear.
 

mentasm

Distinguished Member
As I said, apologies if I misinterpreted your statement, which I obviously did. I thought you were saying that discs had to include uncompressed PCM tracks, DD tracks and DTS tracks in addition to the other formats. I'm not going to get into a debate about the base audio being PCM for all tracks as I believe that just overcomplicates the issue (as you can see by my confusion over your post). I wasn't ware that some studios put the PCM logo on discs with Master Audio just because the audio is 'technically' PCM. I've certainly not seen it on any of my discs, but then I guess haven't been looking particularly closely.

Anyway, apologies again for the misunderstanding.
 
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dante01

Distinguished Member
Thank goodness I don't have to start explaining pulse-code modulation LOL :D

I thought you were saying that discs had to include uncompressed PCM tracks, DD tracks and DTS tracks in addition to the other formats.

I am and they do. The other formats are optional. PCM, DD and DTS are mandatory.

mandatory |ˈmandəˌtôrē| |ˈmøndəˈtɔri| |ˈmandət(ə)ri|
adjective
required by law or rules; compulsory : wearing helmets was made mandatory for cyclists.
• of or conveying a command : he did not want the guidelines to be mandatory.
 
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MarkusThatch

Distinguished Member
Thank goodness I don't have to start explaining pulse-code modulation LOL :D



I am and they do. The other formats are optional. PCM , DD and DTS are manatory.

So, explain about pulse-code modulation Dante:devil:
 

dante01

Distinguished Member
So, explain about pulse-code modulation Dante:devil:

little nanobots are spread on the disc. These nanobots jump up and down causing vibrations. These vibration travel down through bits of plastic sellotaped to the inside of your player until they reach the wet string interface exchange (WSIE). The more plastic bits the higher the quality of the data tansfer. From the WSIE they are converted into microscopic four wheel drive vehicles that drive out of your player and along the cables to your AV receiver or amplifier. Some of the more expensive players also do the school run.

Some meaningless charts:

chart3.png


barchartvertical.gif
 
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mentasm

Distinguished Member
Thank goodness I don't have to start explaining pulse-code modulation LOL :D



I am and they do. The other formats are optional. PCM, DD and DTS are mandatory.

mandatory |ˈmandəˌtôrē| |ˈmøndəˈtɔri| |ˈmandət(ə)ri|
adjective
required by law or rules; compulsory : wearing helmets was made mandatory for cyclists.
• of or conveying a command : he did not want the guidelines to be mandatory.
I know what mandatory means thank you, but as I've already explained the way I read your original post was that you were saying that all three of the mandatory codecs had to be on the disc in addition to any optional codecs, which is not the case (only one of them has to be on there). I later realised this was not what you were saying after you explained yourself further, and apologised for the misunderstanding. There was really no need for that rather condescending post.
 

scumball

Distinguished Member
I know what mandatory means thank you, but as I've already explained the way I read your original post was that you were saying that all three of the mandatory codecs had to be on the disc in addition to any optional codecs, which is not the case (only one of them has to be on there). I later realised this was not what you were saying after you explained yourself further, and apologised for the misunderstanding. There was really no need for that rather condescending post.

I thought dante01 was also saying that the mandatory codecs had to be included on the BD disc. They don't. The mandatory codecs have to be supported by BD hardware, not software. You can put any audio you like on the disc....

These are the confusing parts:

Whether stated or not, all Blu-ray discs include PCM audio

PCM is mandatory on Blu-Ray as are Dolby Digital and DTS. Master Audio is optional, while you can omit Master Audio, you may not omit PCM, Dolby Digital or DTS. PCM is the mandatory lossless audio format awarded to Blu-ray. Formats such as TrueHD, Dolby Digital Plus and Master Audio may be totally omitted and are optional.

Not all BDs have PCM audio - end of story.
 
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MarkusThatch

Distinguished Member
As for Starship Troopers, I own the UK disc and I'm pretty sure that it only has a PCM soundtrack, but I'll check tonight. It's most probably a just a sleeve error. I don't own the UK edition of The Departed, but reviews state that it's DTS-HD while other regions are PCM (I have the US disc).

I've checked and starship troopers does have the dts hd master audio logo on the back in addition to PCM 5.1 as do crimson tide, con air and there will be blood in my collection. Can't all be mistakes can they?
 

dante01

Distinguished Member
I thought dante01 was also saying that the mandatory codecs had to be included on the BD disc. They don't. The mandatory codecs have to be supported by BD hardware, not software. You can put any audio you like on the disc....

Are you suggesting codeca are encoded onto Blu-ray discs or are you saying I said that?

And no, certain audio formats must be present on a commercially authored Blu-ray movie. Yes, you can put any audio format you want on a blu-ray disc, as long as you also include one or more of the mandatory formats alongside of it or them.

Even the standard definition DVD spec requires all discs contain either a Dolby Digital or PCM soundtrack as the base standard.

The Blu-ray spec requires that either PCM, Dolby Digital or DTS audio be included on the disc.
 
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mentasm

Distinguished Member
The confusion arises from the way it's written. The following statement makes it sound like they all have to be present on the disc:

Master Audio is optional, while you can omit Master Audio, you may not omit PCM, Dolby Digital or DTS.
That is not the case. You have to include one of those (as you have since stated), but not all of them. This is what caused the confusion on my part. If you had used the word 'either' your meaning would have been clear.

Studios use the term 'PCM' on their releases to denote the presence of a PCM soundtrack, not as a catch-all term for the underlying data. Using it in such a fashion would be incredibly confusing to consumers. There is simply no need to overcomplicate the issue by saying 'all audio is PCM'. That's not what they mean when they say a disc has a PCM soundtrack. So when I said 'PCM is always listed when in is available', this is what I was referring to.

This was actually quite a simple issue that got clouded. The situation with Starship Troopers is this: it lists a PCM audio track in the specs and also has a DTS-HD Mater Audio logo. Of the twenty-odd BDs I own that have PCM soundtracks, only Disney discs have Master Audio logo on the sleeves, leading me to conclude that this is something unique to them as a distributor. This conclusion would seem to be supported by the fact that both Crimson Tide and Con Air are Disney (formerly Buena Vista) titles. Of the one hundred and forty odd BDs I own that don't have a PCM track I can't think of a single one that specifically mentions PCM anywhere (just like The Departed makes no mention of it).

Also, this statement:

PCM has to be present! It isn't a codec and it isn't an audio track

directly conflicts with the FAQ on the first page under 'What audio codecs will Blu-ray support?'. However, I'm of the opinion that any attempt to explain HD audio (an already complicated matter) would be best served by keeping things as simple as possible, rather than arguing semantics like 'all audio is PCM'.
 

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