Appletv 2 - passing through HD Audio?

instigator

Active Member
I Know appletv 2 can pass through 6 channel audio via hdmi... But at a quick glance it looks like the handbrake settings are all some form of downsampled audio, even the 6 discrete channel passthrough?

Would I have to somehow import the 6 Channel audio from the mkv file via some other method?

Or can anyone confirm that any of the 5.1 passthrough settings is the exact copy of the audio? There are several options of getting the 5.1 channel audio passthrough as well... Can anyone confirm which is highest quality? Off the top of my head there is core audio, ac3 and maybe 2 more...

Also, will the HD Audio light on my Denon 1610 light up with the audio played via appletv 2 hdmi?

Thanks...
 
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Matt_C

Distinguished Member
Apple TV doesn't support HD audio formats such as Dolby TrueHD or DTS-HD

HE-AAC (V1)
AAC (16 to 320 Kbps)
Protected AAC (from iTunes Store)
MP3 (16 to 320 Kbps)
MP3 VBR
Audible (formats 2, 3, and 4)
Apple Lossless
AIFF
WAV
Dolby Digital 5.1 surround sound pass-through

For ripping media with Handbrake, you select Dolby Digital passthrough to use the unchanged audio track from the movie
 

bpsmith

Well-known Member
Not quite correct. You don't get unchanged audio as far as HD is concerned.

The HD Audio track contains a standard DTS or DD mix which it uses as the downmix source when playing back on non compatible kit like ATV2.

It is as per the original but just not in HD unfortunately. Even the Mac Mini, with HDMI out, doesn't support HD Audio much to my disappointment!
 

instigator

Active Member
Here's the thing... When I'm ripping my collection I just want to do it once so I don't have to do it again when appletv gets upgraded etc... For video i experimented with 1080p as appletv will still play it, it just down converts it to 720p at appletv... But I tested the 1080p rips on my brothers 60" tv via ps3 playback and I couldn't tell a difference in quality between the 720p version... What did make a difference was bumping up the quality of the 720p rips so that I wouldn't get any banding or pixilation on shadows or graduated areas of color...

So for audio... Normally the DD PLII default is something like 128 or 160kbps so I use the HD audio and bump it up as high as it can go to 320

For 5.1 discreet passthrough it defaults on AC3 to 600 something... Which I guess works out to 128 per channel? That can't be good? How is that better?

I browsed around and I think using the Core Audio 5.1 passthrough version can go up to 768 or something? Which I guess is gonna be higher than 128 per channel of the ac3 version?

Why can't I just rip the wave or aiff version and stick that into the video file? I know appletv will play those files on their own but what about within a video file? And wouldn't that yield better audio quality?

I think the Subler app let's one change the audio files but not sure... Can anyone recommend a way of extracting the hd audio from a mkv file and sticking it into a hanbraked video file? On a mac?

I guess a wave or aiff of stereo/Pro Logic II file would be a good compromise over 5.1 channels of aiff?
 

bpsmith

Well-known Member
Passthru the Audio s just that, passthru. It doesn't get touched by HandBrake! Whatever quality nbd bitrate is originally there will stay there.

As far as 1080p is concerned, it is possible to get that to play on ATV but, with the limited bitrate allowed, it won't look as good as a good quality 720p. The line is drawn on the bitrate and using 1080p is the wrong move IMHO as the conversion is not great then.
 

instigator

Active Member
ok, some things that just crystallised for me now messing around with Handbrake...

the normal Non HD audio, if i select that 5.1 track to rip as AC3 passthrough the bitrate options are greyed out... i'm assuming this is because it just grabs the audio files and plops them into my ripped video file without converting them? so although not HD audio it is some sort of 16bit wave or aiff type file?

the problem is that if i choose the HD 5.1 audio file i don't get the the same options... if i choose any of the codec versions (core audio, AC3 etc) to pass through I then have to choose the bitrate... so it must be down converting them from HD?

so unless I can figure out some way of extracting the HD audio from the mkv file would it just be better to use the old school sd 5.1 and pass it through without converting?

also, I figured out that if I choose AC3 and then Pro Logic II i can select a higher bitrate, instead of 320 I can go all the way up to 640... if hard drive space and network speed isn't an issue is this the way to go?

eBh516SM

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this is the default AppleTV 2 setting in Handbrake:
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also, I think I may be misunderstanding the 5.1 6 channels passthrough info displayed in handbrake... 5.1 passthrough at 640kbps - this isn't really dividing 640 between each channel or is it 640 FOR each channel?
 
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bpsmith

Well-known Member
The HD Audio track has an old school DTS or DD track hidden within to auto downmix to if you don't have the right AVR kit that can support it. Therefore the 5.1 track your talking about must be that.

Personally, the studios can convert the audio far better than any of us can at home with HandBrake. I would simply pass thru this and save wasting your time.

If you convert HD Audio to work on ATV it is no longer HD Audio!

As far as Pro Logic II, etc, letting you choose higher bitrates, what's the point in sacrificing 5.1 for 2 Channel!?!

Use the ATV preset and do a test run. Maybe push the quality up a tad but leave the preset for audio as they are. ;-)
 

instigator

Active Member
Passthru the Audio s just that, passthru. It doesn't get touched by HandBrake! Whatever quality nbd bitrate is originally there will stay there.

right, this is why I was wondering why I could choose different bit rates for passing through HD 5.1 audio... it's because Handbrake can't do it at the moment... the SD 5.1 audio pass through greys out the bitrate option because it just copies it without touching/converting/processing file...

so, options are

1. just use the SD 5.1 audio to pass through
2. use the HD 5.1 audio to pass through and figure out which codec gives better quality for down converting to SD.
3. find a way to extract HD audio from mkv and insert it into handbraked video
4. as a compromise just use the codec that lets one rip HD audio into stereo/PLII format at 640kbps instead of the default 320kbps and forget about HD audio
5. wait until handbrake can passthrough HD audio and rip ones collection again

all this because I'm lazy and don't want to rip my collection again when AppleTV is upgraded or I move to another system of playback... ha ha...
 

Matt_C

Distinguished Member
Not quite correct. You don't get unchanged audio as far as HD is concerned.

The HD Audio track contains a standard DTS or DD mix which it uses as the downmix source when playing back on non compatible kit like ATV2.

It is as per the original but just not in HD unfortunately. Even the Mac Mini, with HDMI out, doesn't support HD Audio much to my disappointment!

In Handbrake, if you select Dolby Digital passthrough, you get unchanged Dolby Digital. I didn't say anything about passing through HD audio unchanged - in fact the contrary - I said Apple TV doesn't support HD audio formats, which is why I said DOLBY DIGITAL PASSTHROUGH. Handbrake doesn't have codec support for DTS or HD Audio formats anyway (as far as I know/have seen)
 

instigator

Active Member
I think the problem occurs from Handbrake being unable to handle HD audio in the same way it handles SD 5.1 passthrough...

I'd be happy if Handbrake could passthrough HD 5.1 unconverted and then AppleTV 2 only playing the SD version until firmware update or AppleTV 3 comes out... This would save me the hassle of ripping my movie collection a 2nd time...
 

Matt_C

Distinguished Member
Just done a little research on Handbrake, and I had version 0.9.5, which doesn't have DTS support, the current SVN version does have it, but only in passthrough - no ability to encode use DTS.

So for example, a DVD or movie file that has a DD 5.1 track > HB will let you pass it through as is, or re-encode using AC3 codec to a lower or higher bitrate, or different speaker config (6ch discreet, PLII, etc)

A DVD/movie file with a DTS 5.1 track > HB will allow passthrough of DTS or re-encode to AC3, AAC, FLAC, or Vorbis.
 

bpsmith

Well-known Member
Matt_C said:
In Handbrake, if you select Dolby Digital passthrough, you get unchanged Dolby Digital. I didn't say anything about passing through HD audio unchanged - in fact the contrary - I said Apple TV doesn't support HD audio formats, which is why I said DOLBY DIGITAL PASSTHROUGH. Handbrake doesn't have codec support for DTS or HD Audio formats anyway (as far as I know/have seen)

Whatever. I am done helping people who are rude !
 

instigator

Active Member
Found an interesting yet dated blog on extracting HD audio from blu rays...

http://www.computeraudiophile.com/content/How-Rip-High-Resolution-Blu-ray-Audio

The comments at bottom are interesting... There are apps that extract hd audio...

I guess I just gotta figure out a workflow for mac os for myself...

Makemkv will extract 1080p vid and hd audio... But handbrake is the wink link at the moment because it can't passthrough hd 5.1 like it does SD 5.1...

So I'd need another application or two to extract the hd audio from mkv file and insert it into the 720p handbraked file...

Update, found this on the Makemkv forum,
This functionality is coming to MakeMKV soon - it will be able to do transcoding for certain streams, and these two conversions (DTS-HD/TrueHD)->(LPCM/FLAC) should be implemented as one of the first. For now you can use eac3to to transcode these streams in MKV file, but it works only on windows and will require "hacked" DLLs to do dts-hd decoding.
 
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instigator

Active Member
Dang, just ripped a blu ray disc in handbrake using the SD 5.1 as passthrough instead of the HD 5.1 track which would have been down converted to SD and the SD 5.1 track turned out to be the descriptive audio version... Makes sense I guess if the HD version just plays the core or cut down SD version of it on un-HD hardware.... So looks like I'm just gonna stick to ripping the hd audio into SD audio till I can sort out an HD workflow...

Argh...
 
Bit of a strange reaction - who's been rude?

It seems like BP took your comment to quote regarding Pass throughs.

BP I have seen nothing from Matt that would make me think he was being rude, and can only comment to say that He (and yourself) have always posted helpful comments in this forum, and I am guessing that nothing was implied.
 
Excellent, cant have either of you two missing, otherwise I will have to buy myself an ATV and have to answer all these questions myself :D
 

bpsmith

Well-known Member
Lol. Sounds like your just looking for an excuse to get one...

Having just read this thread back, I too am lost as to what I was taking offence to!?!

My apologies to Matt. :)
 
Nah, I am good thanks, I have a HTPC that caters for my needs and I can stream avi and mkv to my iPad with the whassname app (forgot its name! :blush:) on the rare occasions I need to :smashin:
 

bpsmith

Well-known Member
Theydon Bois said:
Nah, I am good thanks, I have a HTPC that caters for my needs and I can stream avi and mkv to my iPad with the whassname app (forgot its name! :blush:) on the rare occasions I need to :smashin:

No worries.

Have you thought about using Plex on your HTPC now it's available as a Server and a Player on Windows?
 

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