Apple TV and Surround Sound

[cohibadad]

well after a lot of experimentation I have come to the following conclusions:

1. A valid DTS WAV audio track can be added to an M4V video track in QT, saved in a MOV and streamed to TV which will decode properly on a receiver and play 5.1. The trick is to actually make a DTS WAV file from a ripped VOB.
2. the A52Codec listed above does allow QT to use AC3 tracks which can be added to an M4V video track, saved in a MOV and streamed to TV which plays the file but my receiver does not recognize it as AC3. It plays it though. I loaded the component onto the TV also.
3. my handbraked videos with DLPII are not autorecognized by either of my receivers as DLPII. The linked video above is not either. Whether this is due to my receivers, handbrake, HDMI I don't know. But the DTS WAV file is correctly autorecognized.

Summary: Surround sound with TV is a difficult topic.

 

[TuckBodi]

well after a lot of experimentation I have come to the following conclusions:

1. A valid DTS WAV audio track can be added to an M4V video track in QT, saved in a MOV and streamed to TV which will decode properly on a receiver and play 5.1. The trick is to actually make a DTS WAV file from a ripped VOB.
2. the A52Codec listed above does allow QT to use AC3 tracks which can be added to an M4V video track, saved in a MOV and streamed to TV which plays the file but my receiver does not recognize it as AC3. It plays it though. I loaded the component onto the TV also.
3. my handbraked videos with DLPII are not autorecognized by either of my receivers as DLPII. The linked video above is not either. Whether this is due to my receivers, handbrake, HDMI I don't know. But the DTS WAV file is correctly autorecognized.

Summary: Surround sound with TV is a difficult topic.

Have you tried NitoTV with the mplayer option?

 

[tronic72]

"Surround sound with TV is a difficult topic."

well after a lot of experimentation I have come to the following conclusions:

1. A valid DTS WAV audio track can be added to an M4V video track in QT, saved in a MOV and streamed to TV which will decode properly on a receiver and play 5.1. The trick is to actually make a DTS WAV file from a ripped VOB.
2. the A52Codec listed above does allow QT to use AC3 tracks which can be added to an M4V video track, saved in a MOV and streamed to TV which plays the file but my receiver does not recognize it as AC3. It plays it though. I loaded the component onto the TV also.
3. my handbraked videos with DLPII are not autorecognized by either of my receivers as DLPII. The linked video above is not either. Whether this is due to my receivers, handbrake, HDMI I don't know. But the DTS WAV file is correctly autorecognized.

Summary: Surround sound with TV is a difficult topic.

I agree. I think these technical posts only confuse people and blur the real issue. For all the similar technical posts out there, I think your summary is the most apt and accurate regarding Surround Sound on Apple TV.

I think it's best to say that in it's current state, for 99.999% of the population, the Apple TV doesn't support surround sound. I still love mine but I'd just love it more if it had 5.1 surround.

 

[cohibadad]

I agree. I think these technical posts only confuse people and blur the real issue. For all the similar technical posts out there, I think your summary is the most apt and accurate regarding Surround Sound on Apple TV.

I think it's best to say that in it's current state, for 99.999% of the population, the Apple TV doesn't support surround sound. I still love mine but I'd just love it more if it had 5.1 surround.

I agree.

Apple TV is funny with surround sound. My receivers will not autorecognize a surround sound signal from it (blue light doesn't come on and it does not display dolby signal) but if I manually select dolby processing it does sound like it is surround. Receiver does autorecognize every other input as surround. Very odd. Well, for now I will continue to encode with DPLII. Not worth the effort to use AC3 or DTS with questionable returns at this point. I wonder if Apple downloads would be autorecognized and decoded? Has anyone tried this?

 

[Cave Man]

I think it's best to say that in it's current state, for 99.999% of the population, the Apple TV doesn't support surround sound. I still love mine but I'd just love it more if it had 5.1 surround.

I don't think this is really true at all. If you can use Handbrake, then you can get DPLII with the click of a button. The Apple TV preset of Handbrake defaults to DPLII 5-channel surround, provided the DVD has Dolby Digital. All you need next is to add the file to your iTunes library and make sure your ATV is connected to a DPLII-capable receiver. Voila - you have 5-channel surround sound. Depending on the receiver/amp, you can also get pretty good low frequency audio. My Onkyo does a very good job at this.

Your statement is true if you're talking about 5.1 exclusively, but "surround sound" at a minimum is 4-channel (DPL).

 

[Cave Man]

Apple TV is funny with surround sound. My receivers will not autorecognize a surround sound signal from it (blue light doesn't come on and it does not display dolby signal) but if I manually select dolby processing it does sound like it is surround.

This isn't a function of the ATV, it's a function of the audio matrix. The ATV doesn't "tell" the receiver to switch to some decoding algorithm; the receiver should detect it in the audio track if it is programmed to do so. I don't have any "native" sources with DPLII encoded, so I cannot tell if this might be the case with my system.

Receiver does autorecognize every other input as surround. Very odd.

If the receiver is not programmed to detect DPLII and autoswitch to it, it might not be odd at all. My Onkyo autoswitches for DD, Dolby Surround and DTS, even when I'm watching broadcast TV with my Eye TV Hybrid. Regardless, the DPLII light is always on on my receiver.

Well, for now I will continue to encode with DPLII. Not worth the effort to use AC3 or DTS with questionable returns at this point. I wonder if Apple downloads would be autorecognized and decoded? Has anyone tried this?

As far as I know, none of the iTMS videos are encoded in anything other than stereo.

 

[Cave Man]

Download this file (3.3 mb Quicktime H.264 DPLII video) that was extracted from a Dolby Digital AC-3 5.1 video. If your browser opens it in a window, wait until it completely downloads into QT, then save the file from within the browser's Quicktime window by clicking on the little down-arrow in the lower right corner of the QT window.

I've uploaded another file that is the same as the one referenced above. However, this one was encoded with Handbrake to produce an MKV file using H.264 compression and AC3 5.1 AC3 Dolby Digital passthrough. If you have Perian installed on your Mac and play this file through VLC, and your Mac is connected by Toslink to a receiver capable of decoding DD, you will get 5.1 surround sound.

Note, this file is 4.2 mb in size compared to 3 mb in size for the DPLII version. If this rate holds up, then you can expect any Dolby Digital 5.1 movies that might become available on the iTMS to be about 30% larger than non-DD files. As an example, King Kong encoded as DPLII is 2.6 gb, while the AC3 DD version is 3.9 gb. If you make the video 720 HD, you're talking about 3.5 times more video size. I suspect such a movie would be about 10 gb in size. This is the inherent problem with Apple selling such content - we really need better bandwidth for this type of service.

 

[bmb012]

A receiver isn't going to recognize a PLII file as surround, because it really isn't. It's a stereo stream, and the receiver takes audio that sounds like it should be surround (it sounds muffled), and throws it in the back.

By 'encoding' into PLII, all you're doing is ripping the 5.1 track as stereo, and letting the decoder use algorithms to put audio that sounds like it should be in the back in the back, and sounds that are the same in both speakers (like voice tracks) into the center channel.

I actually read somewhere that the 360 now supports aac 5.1 audio with the latest update, but I haven't been able to test out out yet. Don't see why it wouldn't, as it can mix iPod audio into the 2 front channels while sending a 5.1 digital track, the thing is constantly encoding 5.1 in realtime anyway.

 

[tronic72]

I don't think this is really true at all. If you can use Handbrake, then you can get DPLII with the click of a button. The Apple TV preset of Handbrake defaults to DPLII 5-channel surround, provided the DVD has Dolby Digital. All you need next is to add the file to your iTunes library and make sure your ATV is connected to a DPLII-capable receiver. Voila - you have 5-channel surround sound. Depending on the receiver/amp, you can also get pretty good low frequency audio. My Onkyo does a very good job at this.

Your statement is true if you're talking about 5.1 exclusively, but "surround sound" at a minimum is 4-channel (DPL).

"make sure your ATV is connected to a DPLII-capable receiver" Therein lies the problem.

Many Amps don't support this and I for one and not going to change my $2000 Amp because Apple has decided NOT to follow convention and use a commonly used format. When will they learn???

Apple has created many duds by using non popular, or close source standards. Just look at M$ and how unpopular they've become with their closed standards. Remember how expensive peripherals used to be for the mac before they embraced USB? I know ACC is not the same as open or closed source, but the point I'm trying to make is; Apple stuffed up by not following convention with the Apple TVs audio. They used all the right connectors but they didn't get the internals right.

I think it's sad that Apple didn't simply make this product with the same audio support as a $50 DVD player

 

[bmb012]

The biggest problem is that the AppleTV itself doesn't suport aac... it should be able to decode the 5.1 aac and encode it into 5.1 Dolby...

 

[saltyzoo]

"make sure your ATV is connected to a DPLII-capable receiver" Therein lies the problem.

Many Amps don't support this and I for one and not going to change my $2000 Amp because Apple has decided NOT to follow convention and use a commonly used format. When will they learn???

Apple has created many duds by using non popular, or close source standards. Just look at M$ and how unpopular they've become with their closed standards. Remember how expensive peripherals used to be for the mac before they embraced USB? I know ACC is not the same as open or closed source, but the point I'm trying to make is; Apple stuffed up by not following convention with the Apple TVs audio. They used all the right connectors but they didn't get the internals right.

I think it's sad that Apple didn't simply make this product with the same audio support as a $50 DVD player

I must be misunderstanding you. Are you suggesting that DPLII Is unconventional / non standard?

 

[tronic72]

I must be misunderstanding you. Are you suggesting that DPLII Is unconventional / non standard?

Sorry. Upon reading it my post it a bit confusing.

The point i was trying to make is they didn't follow convention. The device should have had the same audio capabilities as the cheapest DVD player does. It should have been simply plug and play. After all, Apple are the masters of Plug & Play devices.

Sorry for the mix up.

 

[displaced]

A receiver isn't going to recognize a PLII file as surround, because it really isn't. It's a stereo stream, and the receiver takes audio that sounds like it should be surround (it sounds muffled), and throws it in the back.

That's not strictly true.

Pro Logic signals do indeed have multiple channels encoded into them at source. It uses phased signals to embed the 2 extra channels within the regular stereo signal. Whilst not as precise as discrete channels, the author still has a certain amount of control over sound positioning in a PLII signal.

For example, (if you've got one), start the Software Update process on a Nintendo Wii. Even with just PLII support, you'll notice the 'connecting' sound sweeps around the listener -- it doesn't just get the muffled bits plonked at the rear.

 

[bentoms]

Cheers for the info Cave Man

I am getting meself an Apple TV for chrimbo, I've waited a while but have relised now that the limitations of my setup actually allow for the apple tv to plug in quite happily!

Limitations are:

My TV is 720p only.
My surround sound system can take DPLII from RCA, & it does this for my Wii.


Being that I have ordered the 80 GB version as I have some 30gb of music & pictures to copy. The only video i'll play through are stuff like prison break etc.. which i download as I cannot afford sky (or the p*ss poor internet connection that i will get, (125k if lucky as am 2.5km from exchange!)).

(Don't worry though as anything that i download i then buy once the dvd boxset is released, it clears my concious anyways!).

So all i need now in a HD Component switch box & i am away!

 

[imlucid]

Being that I have ordered the 80 GB version

I hope that was a typo since there are only 40 and 160 GB versions available from Apple...

Kevin

 

[Cave Man]

"make sure your ATV is connected to a DPLII-capable receiver" Therein lies the problem.

Many Amps don't support this and I for one and not going to change my $2000 Amp because Apple has decided NOT to follow convention and use a commonly used format. When will they learn???

I don't know how many amps/receiver support it, but I suspect it's the great majority of those sold today. I just checked Onkyo's and Yamaha's web sites and all of their home theater receivers do DTS, Dolby Digital and Dolby Pro Logic I and II.

Apple has created many duds by using non popular, or close source standards. Just look at M$ and how unpopular they've become with their closed standards. Remember how expensive peripherals used to be for the mac before they embraced USB? I know ACC is not the same as open or closed source, but the point I'm trying to make is; Apple stuffed up by not following convention with the Apple TVs audio. They used all the right connectors but they didn't get the internals right.

I think it's more complex than this. There is no content from iTMS that is encoded in 5.1 (DTS or DD), thus they don't have the impetus to do it. Adding to this is the almost certain fact that they (or the studios) will have to license DD or DTS audio for iTMS movies/shows. This will undoubtedly add to the cost of the files. Then they would have to add support to Back Row to passthrough the encoded DD or DTS out the optical port to a receiver capable of decoding DD or DTS for 5.1 surround sound. We are all hopeful that this is coming - perhaps at MW in January.

I think it's sad that Apple didn't simply make this product with the same audio support as a $50 DVD player

Yes, it would have been nice if Apple had put 6 audio-out ports for the 5.1 (hell, why not 8? The chip will decode it), but there wasn't any content to permit it. Let's hope something like this eventually comes to fruition - both optical port for passthrough of DD/DTS and discrete output for decoding AAC 6-channel. But the receiver will have to have inputs for these as well. It would be cheapest (for Apple, anyway) to do the decoding in the ATV and have the 6 discrete outputs because then they wouldn't have to license DD or DTS - they could just encode using their existing Quicktime technology (6-channel AAC).

 

[Cave Man]

I've updated the first post with info about VLC, DTOX and MTR for Mac-based home theaters.

 

[Avatar74]

Clarification on Dolby Digital vs. Dolby ProLogic II

I've noticed some folks are confused about why Dolby Digital is not supported but surround sound seems to be coming from the track if they switch to Dolby ProLogic II mode on their receiver. I think this warrants a brief explanation for those interested...

Prior to the creation of Dolby Digital (AC-3) 5.1 channel surround, Dolby Surround was the prevailing format for theatrical surround. Dolby Surround is an analog matrix. I'll get to what that means in a second...

A digital format like AAC is designed to reconstruct an analog signal. Most films that have been encoded as Dolby Digital by the studio also have, for older sound systems, Dolby Surround analog encoding. This means that in addition to the 6 discrete channels of digital information, the surround channels have been embedded in the analog signal of the front left and right channels to be decoded by a Pro Logic decoder.

A moment to explain what matrix encoding actually is...

In the digital world, separate bitstreams can be muxed (multiplexed) into one bitstream of digital data and then demuxed as discrete channels. But in the analog world, the Dolby Labs folks, and others, came across a rather ingenious way to do the same thing with analog signals.

I know this will sound elementary but I want to reinforce the idea here because I don't think it's often really understood what the difference is: A digital signal uses multiple "bits" (binary digits, e.g. 0 or 1) per sample to reconstruct the frequency and amplitude of the source at any given interval. An analog signal directly uses voltage oscillations to represent a signal identical to the source. My reason for repeating this distinction here is to emphasize that one format has to reconstruct the signal from an entirely different storage methodology (pulses of electricity, light or whatever else can be used to burst data), the other format (analog) doesn't need to reconstruct the signal... it IS the signal.

The left and right surround channels are phase-shifted 90 degrees and combined with the left and right front channels. So when the recording is played back on any normal system, only the in-phase signal is heard. But in a ProLogic decoder, the out of phase signal is extracted and sent to the surround channels.

I discovered for myself when purchasing the works of Isao Tomita, one of the early synthesizer pioneers who used Dolby Surround in his sound recordings, that the iTunes versions of these songs had been encoded straight from his Dolby Surround masters. The digital files reconstructed the original analog source which was decodable by my Dolby Digital processor (all Dolby Digital processors by default have the ability to decode Dolby Surround analog in a ProLogic mode).

So what you're experiencing can be one of two things... If no surround matrix is present, the decoder is taking any out of phase information and sending it to the surrounds. This has an unpredictable, muddy effect. If you can distinctly hear surround but not quite as clearly as Dolby Digital, and you're watching a movie, then chances are the Dolby Surround analog mix was encoded into the AAC and reconstructed upon playback.

You'll also find that virtual surround encoding methods such as Qsound are perfectly realizable through a system like AppleTV because they are analog methodologies... except virtual surround methods do not require decoding because they rely on perceptible phase shifts of stereo signals to create illusions of spatial characteristics.

 

[wmealer]

All this talk about surround sound from the audiophiles...

Don't get me wrong, I'm all for Apple adding as many features to this magical little box as possible. But I can't help but keep my feet planted firmly in reality. We all know Apple has already called this project a "hobby." Do we really expect them to try to compete in the higher-end home theater market with a hobby?

Apple is all about appealing to the masses, not to the niche markets who know the difference between Dolby TrueHD, DTS, THX, DD, PLII, and so on. They are more concerned that tv works in as many homes as possible (with as little fuss as possible), than pleasing those of us who want the best home theater experience possible. That's a lot to ask from this tiny silver box in my entertainment armoire, which even has trouble streaming low-level 720p content without some sort of hiccup.

 

[Cave Man]

I discovered for myself when purchasing the works of Isao Tomita, one of the early synthesizer pioneers who used Dolby Surround in his sound recordings, that the iTunes versions of these songs had been encoded straight from his Dolby Surround masters. The digital files reconstructed the original analog source which was decodable by my Dolby Digital processor (all Dolby Digital processors by default have the ability to decode Dolby Surround analog in a ProLogic mode).

Wow, that's very interesting. Can you recommend half a dozen songs from him that are encoded in such a way and also available on iTMS? I'd like to download a few and give them a try.

I also understand that Pink Floyd'd Dark Side of the Moon was recorded in quadrophonic. Have you heard if it's made its way to DPLII? That would be completely cool (or better yet, 5.1 DD).

 

[diamond.g]

Encoding DTS/DD in software is incredibly expensive, I would be impressed if Apple went that route.

I don't think downloading multi gig files is that much of an issue, if the ATV were to allow purchasing of the content from it and allowed streaming of partially downloaded files (think 360). Batman Begins on Xbox Live in HD is 5 or 6 gig, which is easily downloaded overnight. I am sure Apple has the resources to ensure optimum speeds are achieved.

 

[Cave Man]

Encoding DTS/DD in software is incredibly expensive, I would be impressed if Apple went that route.

I'm sure that'll increase the cost of downloads from iTMS; if they ever show up.

Batman Begins on Xbox Live in HD is 5 or 6 gig, which is easily downloaded overnight. I am sure Apple has the resources to ensure optimum speeds are achieved.

That's very encouraging. Is this 720 with DD, DTS or some other true 5.1 audio? I did my calculations based solely on ratios of AC-3 to stereo DPLII and DVD-quality to 720 video. I didn't consider frame or bit rates at all. Let's hope Apple can (and will) do something similar and keep that file size down to 5 or 6 gigs - that would be very manageable.

 

[diamond.g]

I'm sure that'll increase the cost of downloads from iTMS; if they ever show up.



That's very encouraging. Is this 720 with DD, DTS or some other true 5.1 audio? I did my calculations based solely on ratios of AC-3 to stereo DPLII and DVD-quality to 720 video. I didn't consider frame or bit rates at all. Let's hope Apple can (and will) do something similar and keep that file size down to 5 or 6 gigs - that would be very manageable.

Oddly, I just looked on live and can't seem to find Batman Begins or Superman Returns. I found TMNT and it is 720p with 5.1 audio and it is only 4GB. Meet the Robinsons is only 4.3GB. 300 is 5.3 GB.

I just figured out why I can't find the other two, it looks like MS rotates movies. Movies seem to be available for a certain period of time. That could be another place Apple could do better.

 

[Cave Man]

Oddly, I just looked on live and can't seem to find Batman Begins or Superman Returns. I found TMNT and it is 720p with 5.1 audio and it is only 4GB. Meet the Robinsons is only 4.3GB. 300 is 5.3 GB.

That's excellent news. What is the audio codec for your 5.1 - DD or DTS (or something else)? Meet the Robinsons from iTMS (640x360, stereo, subtitles) is 1.09 gigs, so if Apple can get DD or DTS issues resolved, it looks like we could get 720 HD/5.1 surround movies at a reasonable size.

 

[diamond.g]

That's excellent news. What is the audio codec for your 5.1 - DD or DTS (or something else)? Meet the Robinsons from iTMS (640x360, stereo, subtitles) is 1.09 gigs, so if Apple can get DD or DTS issues resolved, it looks like we could get 720 HD/5.1 surround movies at a reasonable size.

Pretty sure it is DD.