Apple TV and 5.1 support - some definitive answers

[incubowski]

That is great to hear. Especially for Apple TV owners, as it will sound better than the downmix of 6-channel AAC. Great work! I guess the developers forum is where to look for an announcement of when the latest svn will include this.

EDIT: Is there a place where I can check to see if the SVN build I have is mixing 5.1 AC3 to DPL1? Is there somewhere on trac, or a build number in the svn compiled version to allow me to see how it is handling 5.1 AC3?

[nightstrm]

Very good to hear... DPL2 is a great alternative to DD, and the results can be pretty impressive. With this and the anamorphic setting, I'll finally have a quick and convenient way of ripping my DVDs at the best quality for AppleTV.

[maurj]

incubowski: there was a bug in recent revs in the svn, which meant that Handbrake wasn't downmixing to DPL I (it was just using stereo). This will have affected all revs since rev 438. I fixed this today in rev 472, so the svn version of Handbrake is once again downmixing to DPL I.

I've been working on the DPL II mixing today, and whilst I don't have anything to check in yet, I have created a sample DPL II file, ripped with my dev copy of Handbrake. You can download it from here:

http://www.maurj.com/5_1_DOLBY.htm

The first test file is encoded as DPL I, with 4.0 channels
The second test file is encoded as DPL 2, with 5.0 channels
With the second one, if you set your amp to expect DPL II, you should hear separate left and right surround channels.

Please do give it a try and let me know how it sounds!

- maurj.

[incubowski]

Great! I will definitely give the sample a try when I get home from work. I am so happy to hear their may soon be DPL2 output from handbrake. IMHO it is the best option for ripping DVDs for use with Apple TV, and ever since I read what Apple TV's audio capabilities were I immediately suggested DPL2 would be a good option. I never expected progress to be made so quickly. 6 channel aac might be better in the future but it just isn't right now. I have had a great time using handbrake the last couple weeks to find the best way to get my DVDs on Apple TV. I have settled on using the anamorphic setting with the svn build and choosing 74% (with CRF enabled), and it really does look the same as the DVD to me. The sound was the only sacrifice being made, but with DPL2 I think the differences between DVD and the .m4v file will be absent as far as most people can tell. I have literally had the DVD player (upscaling player) and Apple TV playing the same movie at the same time and been switching back and forth sitting 3 feet from a 52 inch Sony HDTV (720p) and I can't tell the difference. Can't wait to compare the sound between DPL2 and an actually 5.1 AC3 track from the DVD. Furthermore, with the chapter feature working I could not be happier. Anyway, sorry to drag on, thanks for looking into DPL2, can't wait to test it.

[maurj]

BTW, I found out how QuickTime and Apple TV are creating the separate "center" channel from a 6-channel AAC track. It's actually very very simple. All they do is to split the 'center' channel over left and right - outputting exactly the same information to both left and right. (This is pretty much all they can do, really). What I hadn't realised is that this is also how Dolby Surround encodes a center track. Dolby Surround looks at the Left and Right channels and tries to find any signal which is common to both. This is extracted as a center track. So this is how the Apple TV is doing it's "3.0 mix"

- maurj

[AJK]

incubowski: there was a bug in recent revs in the svn, which meant that Handbrake wasn't downmixing to DPL I (it was just using stereo). This will have affected all revs since rev 438. I fixed this today in rev 472, so the svn version of Handbrake is once again downmixing to DPL I.

I've been working on the DPL II mixing today, and whilst I don't have anything to check in yet, I have created a sample DPL II file, ripped with my dev copy of Handbrake. You can download it from here:

http://www.maurj.com/5_1_DOLBY.htm

The first test file is encoded as DPL I, with 4.0 channels
The second test file is encoded as DPL 2, with 5.0 channels
With the second one, if you set your amp to expect DPL II, you should hear separate left and right surround channels.

Please do give it a try and let me know how it sounds!

- maurj.

Sounds like you're doing some great work there.

What are the implications for file sizes using DPL 2? I know nothing about such things but I'm just wondering if DPL 2 results in significantly bigger files when encoding to a comparable level of quality with standard stereo or 5.1 AAC for example.

[maurj]

AJK: DPL I and DPL II files are just stereo. They're no bigger than a stereo track, because they are a stereo track. You might want to use a higher bitrate, maybe - that's the only way they'd make it bigger.

[sd51]

Maurj, you rock!

Thank you for your excellent contributions to this system. Keep up the good work!

AJK: DPL2 is, technically, just a two-track audio mode. So, you can encode it to whatever bitrate you want. I think if you drop it below 128kbps, though, you might lose the matrix encoding. I'd say that if you took a Dolby Digital 5.1 soundtrack, which maxes out at 448kbps, and transcoded it to a 256kbps AAC DPL2 soundtrack, you're cutting the bitrate in half and getting very comparable audio quality.

[maurj]

sd51: no problem!

So has anyone tried my test DPL II encode file? The link is listed a few posts back in this thread. I'm keen for a few people to try it on their DPL II decoders / amps before I consider commiting any code...

- maurj

[sd51]

maurj, I'll be happy to test it the minute my Fosgate FAP T1+ arrives (1-2 weeks). Until then, I'm embarrased to say that my current system only supports DPL1.

[deckeda]

maurj is my new favorite super hero. sd51, you're his sidekick. You guys decide on the "super suits" but remember what Edna Mode said: No capes!

[kalfalfa]

the samples work good for me - the DPL II definitely separates the two rear channels. keep up the good work!

[jonathankit]

Ok, so I can't really test anything because a) don't have my receiver yet and b) don't have apple tv... I've skipped over all of the test files for that exact reason. So today I had time to kill and downloaded two of maurj's files (the last two on the linked page above.. DPLI and DPLII) and played them through the Apple HiFi via optical out on my MBP. Just sat directly infront of it and closed my eyes while listening. With the DPLI I could hear left, centre and right.. the left and right surround sounded the exact same. With the DPLII I could hear left, right, centre, left surround and right surround... each in different "locations".
I'm pretty sure that means absolutely nothing, but just thought I would pass the info along incase it was useful.

[Anamonde]

I downloaded the clip called dts_diatonis_io_afos. which one did you try?

Same one here.

Maurj: That file does not want to sync with the appleTV. It tells me that it is not a file that the appleTV can play... (which is of course rubish, cause I have perian / a52 installed).

PLII = 5.0? Would it be possible to encode a PLII.1 file? In other words a PLII like you are doing now that the receiver will decode into 5.0 and an extra LFE track for the subwoofer. So when I hit command+j in quicktime it will show me three channels. The stereo PLII and a LFE channel. Would that work?

[AJK]

To maurj and sd51,

Thanks, I understand about DPL I and II essentially being stereo but when talking about file size I'm assuming we need to use higher bit rates to maintain a decent quality across the additional surround channels.

Thanks sd51 for the extra info. 256kbps seems reasonable and I'm already using that for my concert DVDs.

I'm getting the impression that DPLII is going to be the way to go for the forseeable future with AAC 5.1 something to look forward to when there's hardware support and downmixing isn't required.

Keep up the great work maurj and anyone else involved in developing and testing.

[maurj]

Anamonde: did you try the file called "dts_diatonis_io_afos", which someone else had referred to? Because I didn't mean that file at all - I'm interested to see how people get on with the last file on this page:

http://www.maurj.com/5_1_DOLBY.htm

The file I mean is 5_1_DOLBY_dpl2_192kbps.m4v, which is my Dolby Pro Logic II file (created here with a local dev copy of Handbrake). Does this play with separate left and right surround on your amp? Does it sync with your Apple TV?

[rigormortis]

Hi maurj,
I gave your dp2 and dp1 files a try and they would not sync with my Apple TV either. They would also not sync. I get an error in iTunes that states "5_1_DOLBY_dp1_192kps was not copied because the video format is not supported by the Apple TV".

They do play in iTunes on my G5 however.

[rigormortis]

I was able to convert the video using quicktime's export to apple TV setting. It will now sync and play on my atv, however the dl2 file gives me the same signal for both of the rear channels. It could be that my receiver does not handle dl2 even though it does dl1, dts, and dd5.1. I'm checking the manual....

[rigormortis]

Yep, my Sony receiver (STR-DE925) does not seem to do dl2

[Anamonde]

The file I mean is 5_1_DOLBY_dpl2_192kbps.m4v, which is my Dolby Pro Logic II file (created here with a local dev copy of Handbrake). Does this play with separate left and right surround on your amp? Does it sync with your Apple TV?

Ya, thats the one I tried. It does not sync with the appleTV.
My receiver is rated for DTS/AC-3/DPL I/II.

[maurj]

Thanks to everyone for testing these - very annoying that they won't sync with the Apple TV. However, my Apple TV arrives later today, so I'll experiment with that and post some revised files once I know that they definitely sync

- maurj.

[neptune2000]

[...]

http://www.maurj.com/5_1_DOLBY.htm

The first test file is encoded as DPL I, with 4.0 channels
The second test file is encoded as DPL 2, with 5.0 channels
With the second one, if you set your amp to expect DPL II, you should hear separate left and right surround channels.

Please do give it a try and let me know how it sounds!

- maurj.

Only the first of the 4 files will load on Apple TV. It plays OK the left, right and center, but the left and right surround play on the regular left and right. All other are higher than the 160k and ATV will refuse to download or stream them.

[neptune2000]

Anamonde: did you try the file called "dts_diatonis_io_afos", which someone else had referred to? Because I didn't mean that file at all - I'm interested to see how people get on with the last file on this page:

http://www.maurj.com/5_1_DOLBY.htm

The file I mean is 5_1_DOLBY_dpl2_192kbps.m4v, which is my Dolby Pro Logic II file (created here with a local dev copy of Handbrake). Does this play with separate left and right surround on your amp? Does it sync with your Apple TV?

Apple TV max out at 160kbps. iTunes will not serve it to Apple TV.

[maurj]

neptune2000: I actually think there's something wrong with the video in my original files, which is preventing it from syncing. Thankfully, my Apple TV arrived today, so I've been able to create some files which I know definitely work

I've updated my page with new files:

http://www.maurj.com/5_1_DOLBY.htm

They're 160kbps now (although I don't think this was the problem). They play in DPL I and DPL II respectively on my amp here from the Apple TV Please, please do give them a try yourself and see what results you get!

- maurj

[Anamonde]

I've installed Perian and The ATVFiles plugin on my AppleTV.
With those installed your DPL II 192kbps files play fine (although the files still do not sync via iTunes)... but not everyone is going to hack open the appleTV... so not really a good sollution.