AppleTV to support Dolby5.1 Natively

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sbalthazor
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AppleTV to support Dolby5.1 Natively

Post by sbalthazor »

Watching the kynote from MacWorld and it looks like they are supporting 5.1 Dolby Digital on the AppleTV natively (via a software upgrade - no more hacks required). Apparently someone figured out that no one would want to pay $2.99 for a rental in DolbyProLogic...

Wondering how and the format, but I'm hoping that means I can start getting ready to rip my entire DVD collection! Can't wait for the softare update to start playing (the keynote said it would be 2 weeks before it was delivered)...

jbrjake
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Re: AppleTV to support Dolby5.1 Natively

Post by jbrjake »

Note that we still don't know if "Dolby 5.1" means "Dolby Digital 5.1" (AC3, like on a DVD) or "Dolby's AAC with 5.1 channels, converted to AC3 and send over the optical out in real time"....

The latter would be better for HB, as it already does AAC 5.1 and it's standards-compliant. While AC3 would mean they're moving back to .mov, as .mp4 doesn't really support AC3.

Cavalicious
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Re: AppleTV to support Dolby5.1 Natively

Post by Cavalicious »

From the new specs page:
Audio formats supported

* AAC (16 to 320 Kbps); protected AAC (from iTunes Store); MP3 (16 to 320 Kbps); MP3 VBR; Apple Lossless; AIFF; WAV; Dolby Digital 5.1 surround sound pass-through

jbrjake
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Re: AppleTV to support Dolby5.1 Natively

Post by jbrjake »

Cavalicious wrote:From the new specs page:
Hmm...this could be a difficulty, if it means cramming AC3 into mpeg4ip's muxer :/

nightstrm
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Re: AppleTV to support Dolby5.1 Natively

Post by nightstrm »

This is sure interesting, and if that statement is actually correct, not how I expected them to handle this. Oh well, if that's the case, I'll just have to start re-encoding yet again... I wonder how iPhone/iPod would like a DD5.1 soundtrack though (maybe that's why they added the ability to change audio tracks)?

rmilchman
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Re: AppleTV to support Dolby5.1 Natively

Post by rmilchman »

I'm new to this environment. What settings would I use in HB for video / audio? Would this ripped media also be playable using VLC (on a Mac) through stereo speakers?

Rich

lordeagle
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Re: AppleTV to support Dolby5.1 Natively

Post by lordeagle »

First a little disappointment: the AppleTV is still limited to 720 videos :(

Now, let's go technical. What is it about the MP4 container that it doesn't support (or not well) an AC3 soundtrack?

lordeagle
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Re: AppleTV to support Dolby5.1 Natively

Post by lordeagle »

rmilchman wrote:I'm new to this environment. What settings would I use in HB for video / audio? Would this ripped media also be playable using VLC (on a Mac) through stereo speakers?

Rich
Rich... without knowing what your target "platform of choice" for watching the videos is, it's impossible to say. It's like asking which airline we recommend, but you won't say where you want to go.

Personally, I use VLC on Windows and so far it's played everything I've encoded with HandBrake.

rmilchman
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Re: AppleTV to support Dolby5.1 Natively

Post by rmilchman »

OK sorry for the confusion, let me try again.

I currently have a dlink dsm-520 that I'm considering replacing with an AppleTV. For storage / iTunes presentation I have a Buffalo Terastation Live (2 terabyte raid 5) I have a Harmon/Kardon receiver and plan on connecting the unit via fiber to allow for Dolby Digital 5.1. I had read in the past that playing or ripping Dolby Digital was not exactly easy with the AppleTV. Will this new "Software" make it easier? If so what settings would I use within HB to create the file?


The file created, will it play on both AppleTV and my mac (using VLC and stereo speakers)?


Does that help with my question?

jbrjake
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Re: AppleTV to support Dolby5.1 Natively

Post by jbrjake »

lordeagle wrote:Now, let's go technical. What is it about the MP4 container that it doesn't support (or not well) an AC3 soundtrack?
You have to tell a muxer what it's muxing.

There is no way to tell mpeg4ip how to mux AC3 right now. You can't tell it "You're muxing AC3 audio" because it doesn't know what AC3 audio is like. The term is not in its vocabulary, and it doesn't have code to handle it.

This is because AC3 is not part of the MP4 standard, which is a matter of ISO politics more than technicalities -- .mov, of which .mp4 is a subset, supports AC3 fine.

There just aren't any open source muxers that violate the MP4 standard, so someone will have to patch one of them (preferably mpeg4ip, as it's what we use) to do so.

Considering mpeg4ip is a dead, unmaintained project, this will all be solo work on the part of whoever takes it on (if anyone does).

Can someone please tell me why people are in this thread asking for technical support with something HandBrake can't yet do, and might not ever do? This could be a useful topic for centralizing research into shoehorning AC3 into MP4, but not if people abuse it to ask stupid questions like "Can VLC downmix AC3 for stereo speakers?"

nightstrm
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Re: AppleTV to support Dolby5.1 Natively

Post by nightstrm »

lordeagle wrote:First a little disappointment: the AppleTV is still limited to 720 videos :(

Now, let's go technical. What is it about the MP4 container that it doesn't support (or not well) an AC3 soundtrack?
Downloading 1080p videos (rentals) would be unbearably long, and probably suffer from over-compression. 720p is as good as its going to get until broadband speeds across the nation come up. There is nothing wrong with 720p; the majority of people out there sit way too far from their HDTVs to notice anyways.

jbrjake
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Re: AppleTV to support Dolby5.1 Natively

Post by jbrjake »

Again, can we please try and stay on topic?

AppleTV + Dolby 5.1

lordeagle
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Re: AppleTV to support Dolby5.1 Natively

Post by lordeagle »

rmilchman wrote:OK sorry for the confusion, let me try again.

I currently have a dlink dsm-520 that I'm considering replacing with an AppleTV. For storage / iTunes presentation I have a Buffalo Terastation Live (2 terabyte raid 5) I have a Harmon/Kardon receiver and plan on connecting the unit via fiber to allow for Dolby Digital 5.1. I had read in the past that playing or ripping Dolby Digital was not exactly easy with the AppleTV. Will this new "Software" make it easier? If so what settings would I use within HB to create the file?


The file created, will it play on both AppleTV and my mac (using VLC and stereo speakers)?

Does that help with my question?
For now you can use the AppleTV present (personally I've decided to now stick to 1500kbps for the video...350Megs for a 40min episode gives me a much lower quality, I tested it this morning -- but of course anyone else can tell you that)..the problem you read remains regarding Dolby Digital. I bet it'll be a while before our friends here can shove an AC3 stream into an MP4 file. My guess though, is that we'll first see how Apple's doing it (meaning are they going back to mov or they going to break the mp4 standard?). From there, decision will probably be made in the community as to how they're going to replicate that behavior or simply not bother with at all.

I'm pretty excited about some of the updates for the AppleTV...and I almost wanna go get one at the new price tonight...but at the same time I'm worried about the surround sound for it. If HandBrake has to break the mp4 standard to have AC3 in it, that means those files probably won't be playable on other devices. UUUUUUUUGH! Why does it have to be so complicated?

(jbrjake feel free to delete my post if you think it's too off subject)

rmilchman
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Re: AppleTV to support Dolby5.1 Natively

Post by rmilchman »

jbrjake wrote:
lordeagle wrote:Now, let's go technical. What is it about the MP4 container that it doesn't support (or not well) an AC3 soundtrack?
You have to tell a muxer what it's muxing.

There is no way to tell mpeg4ip how to mux AC3 right now. You can't tell it "You're muxing AC3 audio" because it doesn't know what AC3 audio is like. The term is not in its vocabulary, and it doesn't have code to handle it.

This is because AC3 is not part of the MP4 standard, which is a matter of ISO politics more than technicalities -- .mov, of which .mp4 is a subset, supports AC3 fine.

There just aren't any open source muxers that violate the MP4 standard, so someone will have to patch one of them (preferably mpeg4ip, as it's what we use) to do so.

Considering mpeg4ip is a dead, unmaintained project, this will all be solo work on the part of whoever takes it on (if anyone does).

Can someone please tell me why people are in this thread asking for technical support with something HandBrake can't yet do, and might not ever do? This could be a useful topic for centralizing research into shoehorning AC3 into MP4, but not if people abuse it to ask stupid questions like "Can VLC downmix AC3 for stereo speakers?"

I guess the rule of there is no stupid except the unasked doesn't apply? I always thought forums are a great resource to learn and communicate. I guess your above learning or attempting to help others.

dynaflash
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Re: AppleTV to support Dolby5.1 Natively

Post by dynaflash »

rmilchman wrote:I guess your above learning or attempting to help others.
Nope, he just wants to stay on topic. Biggest issue with a forum thread being useful as per the topic is when it starts wandering all off course. Then its almost impossible to follow. jbrjake is just keeping the topic of this thread on track as he should. This will be a *very* hot topic as the new appleTV software comes closer to being released.

Back on topic: I suppose its way to much to ask that apple might use 5.1 aac which HandBrake aready encodes eh ? ;)

rhester
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Re: AppleTV to support Dolby5.1 Natively

Post by rhester »

I'm not sure I really understand the speculation. Apple TV content provided through the iTunes Store from day one has been in a MOV container rather than MP4...so why is anyone confused about how Apple "might handle this"? It will be AC3 in a MOV. The question, if there is one, for the HandBrake team is to decide whether they would rather "bastardize" MP4 to support AC3 or whether they'd rather support output in a MOV container. Neither is trivial.

Rodney

Anamonde
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Re: AppleTV to support Dolby5.1 Natively

Post by Anamonde »

I'm putting money on the AppleTV using AAC with 5 channels in the .m4v file... same as the movie trailers from apple.com/movies

AAC -> AC3 on the fly over toslink + HDMI

Why do I think this?
AC3 stream is too large to to transfer over interweb
Last edited by Anamonde on Wed Jan 16, 2008 4:23 pm, edited 1 time in total.

roundy

Re: AppleTV to support Dolby5.1 Natively

Post by roundy »

Ok, I sort of understand from the developers that it may be hard to replicate what Apple is doing with the new HD + DD 5.1 iTunes movies. Here is my question:

Handbrake 0.9.1 can already output the following - AVC/H.264 Video/ AC-3 Audio. But it can only do this as a .mkv or .avi file. Why would it be so hard to do it as a .mov file?

Please forgive my ignorance on the technical aspects of mpeg4 encoding. If I understand the terms "muxing" and "demuxing" correctly, I'm just thinking that perhaps "muxing" doesn't need to be done in the end.

My guess would be that Apple is just encoding the video as H.264 and "copying/attaching" the AC-3 audio to the resulting file. I suppose the hardest part would be to keep them in sync. But, then again, we don't know what Apple is using as the source, probably not MPEG2 from a DVD. The most obvious downside is that the resulting file will not play on an iPhone or iPod. But since Apple is not allowing movie rentals to be moved around, perhaps they dont' see this as a problem. It could be that the new HD movies are AppleTV or iTunes on Mac/PC only.

Did anyone notice if Apple will allow HD + DD 5.1 movie rentals on iTunes or is it AppleTV only? Just wondering if someone will be able to get one of these files on a computer in order to "reverse engineer" it. Perhaps that will shed some light on what Apple is doing.

Just my $0.02

roundy

Cavalicious
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Re: AppleTV to support Dolby5.1 Natively

Post by Cavalicious »

But since Apple is not allowing movie rentals to be moved around
Just watched the keynote, and SJ said you can move them around.

dynaflash
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Re: AppleTV to support Dolby5.1 Natively

Post by dynaflash »

roundy wrote:Please forgive my ignorance on the technical aspects of mpeg4 encoding. If I understand the terms "muxing" and "demuxing" correctly, I'm just thinking that perhaps "muxing" doesn't need to be done in the end.
Um, "muxing" *must* be done in the end if you want a. a movie with sound and b. a movie that is readable. If we don't mux the audio and video you will get ... nothing worthwhile.

roundy

Re: AppleTV to support Dolby5.1 Natively

Post by roundy »

"We've also learned that HD movie rentals will be available exclusively through the Apple TV, and considering that only rentals made from iTunes can be moved to other devices, any downloads originating from the Apple TV (including everything in high-definition) won't be making their way onto your iPod, iTunes library, etc."

That is a quote from Engadget regarding the HD movie rentals. Also, a quick and dirty search through iTMS today reveals no HD movies for rent. To be sure, I only picked a few easy to find movies to check (Ratatouille, 300, etc.) and none of those offered an HD rental option. I guess Apple won't make this that easy after all. I suppose someone with a hacked AppleTV will be able to FTP into it and transfer the file out.

Thanks for the explanation dynaflash. So, I guess the problem then is muxing h.264 video and AC-3 audio into a .mov container? As I understand jbrjake, Handbrake's current mp4 muxer (mpeg4ip) doesn't understand how to handle AC-3. And since the mpeg4ip project is no longer being worked on, an update is unlikely.

So here then is another possibly stupid question. Considering that it is possible to have Handbrake output AVC/H.264/AC-3 in an .mkv or .avi file. Is there anyway to convert that file into a .mov file? Just wondering if anyone knows about any tools to do that in general or if it's even possible. Without screwing up the audio/video of course.

And, this part is just idle speculation on my part, anyone know what kind of tools Apple uses for this kind of work? I would assume it's some proprietary Apple-internal-use-only stuff.

roundy

Cavalicious
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Re: AppleTV to support Dolby5.1 Natively

Post by Cavalicious »

Cavalicious wrote:
But since Apple is not allowing movie rentals to be moved around
Just watched the keynote, and SJ said you can move them around.

"Moved around" doesn't only apply to iPods or AppleTV. You can rent a movie on your iMac, watch some of the movie, copy over to your laptop, get on a plane and finish watching your movie. Hence, "moved around" from one device to another.

This is the example given during the Keynote. I would have to watch again to be 100% sure he was talking about HD.


Either way this topic doesn't belong in this thread.

milo
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Re: AppleTV to support Dolby5.1 Natively

Post by milo »

roundy wrote:Also, a quick and dirty search through iTMS today reveals no HD movies for rent. To be sure, I only picked a few easy to find movies to check (Ratatouille, 300, etc.) and none of those offered an HD rental option. I guess Apple won't make this that easy after all. I suppose someone with a hacked AppleTV will be able to FTP into it and transfer the file out.
From what I understand, the HD rentals are only available from the aTV, meaning they don't appear in iTunes and can only be rented directly from the aTV interface. So to get a file to compare, someone will have to rent one using a new aTV or an old one updated with the new software (said to be released in a couple weeks) and transfer the file back to a computer using ftp or another hack to analyze it.

I have no doubt that this will be a hot topic, there will be plenty of people looking to rip DVDs with 5.1 intact and play it via aTV. Might warrant a sticky topic or FAQ.

jbrjake
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Re: AppleTV to support Dolby5.1 Natively

Post by jbrjake »

rhester wrote:Apple TV content provided through the iTunes Store from day one has been in a MOV container rather than MP4...so why is anyone confused about how Apple "might handle this"? It will be AC3 in a MOV.
As I told rhester on IRC, I'm not so sure of this.

If you download a .mov from the QT HD Gallery on Apple's website, and do an mp4dump, you will see:

Code: Select all

 type ftyp
  majorBrand = qt  
  minorVersion = 537199360 (0x20050300)
   brand = qt  
But if you download an .m4v from the iTunes store, and do an mp4dump, you will see:

Code: Select all

 type ftyp
  majorBrand = M4V 
  minorVersion = 0 (0x00000000)
   brand = M4V 
   brand[1] = mp42
   brand[2] = isom
   brand[3] = 
According to Apple's specs on QuickTime's file format, a brand of qt means mov, and if it isn't present, QT will treat it as whatever it identifies as:
http://developer.apple.com/documentatio ... ion_5.html
Major_Brand
A 32-bit unsigned integer that should be set to 'qt ' (note the two trailing ASCII space characters) for QuickTime movie files. If a file is compatible with multiple brands, all such brands are listed in the Compatible_Brands fields, and the Major_Brand identifies the preferred brand or best use.

Minor_Version
A 32-bit field that indicates the file format specification version. For QuickTime movie files, this takes the form of four binary-coded decimal values, indicating the century, year, and month of the QuickTime File Format Specification, followed by a binary coded decimal zero. For example, for the June 2004 minor version, this field is set to the BCD values 20 04 06 00.

<snip>

If none of the Compatible_Brands fields is set to 'qt ', then the file is not a QuickTime movie file and is not compatible with this specification. Applications should return an error and close the file, or else invoke a file importer appropriate to one of the specified brands, preferably the major brand. QuickTime currently returns an error when attempting to open a file whose file type, file extension, or MIME type identifies it as a QuickTime movie, but whose file type atom does not include the 'qt ' brand.

Note: A common source of this error is an MPEG-4 file incorrectly named with the .mov file extension or with the MIME type incorrectly set to “video/quicktime”. MPEG-4 files are automatically imported by QuickTime only when they are correctly identified as MPEG-4 files using the Mac OS file type, file extension, or MIME type.

If you are creating a file type that is fully compatible with the QuickTime file format, one of the Compatible_Brand fields must be set to 'qt '; otherwise QuickTime will not recognize the file as a QuickTime movie.
According to http://www.ftyps.com/ , qt gets a mimetype of video/quicktime, whereas mp42 and m4v and isom get a mimetype of video/mp4.

To me, this indicates Apple *is* using MP4 with non-standard extensions.

Of course, at some level this is all semantics, since all MP4 is, is a stripped down MOV. How many things do you have to add back in before it stops being a MP4 is a question akin to Theseus' paradox.

zedsdead
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Re: AppleTV to support Dolby5.1 Natively

Post by zedsdead »

First, Apple is only allowing rentals that are downloaded from iTunes directly onto your computer to be moved around. Non from the Apple TV (particularly the HD ones) are going to be available on the computer which is terrible.

I also have been testing the rentals, and I tried the Simpsons movie, and the file is 853x352 or something close to that...Since it plays on the new iPods and iPhone, it seems as though Apple as once again increased the minimum requirements that the iPhone and iPods can play. However, the Apple TV presets (which you get when renting directly from the Apple TV) still do not play on the iPhone as I have just tested that.

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