Apple TV and Surround Sound

Discussion in 'Apple TV and Home Theater' started by Cave Man, Nov 14, 2007.

  1. macrumors 604

    Cave Man

    #1
    (Updated 15 March, 2008)

    With the Apple TV 2 update, Dolby Digital 5.1 surround sound in now possible. This post provides information about how to get your system set up for 5.1 surround sound. If any of this is incorrect, I welcome and appreciate corrections by other forum members. As new information becomes available, I will revise this post.

    1. Definitions

    A. Dolby Digital AC-3 (DD). This is usually 6 channels (termed '5.1') that is sent over a digital connection, either by HDMI or optical cables from the Apple TV to a receiver with the respective inputs. The channels for DD are L, R, C, Rr, Lr and the low frequency LFE channel. The LFE is the '.1' channel.

    B. Dolby Pro Logic II (DPLII). This is a 5-channel surround signal that can be sent over analog or digital connections. The 5 channels are R, L, C, Rr and Lr. DPLII also can be encoded and transmitted over stereo (i.e., 2 lines, right and left) cables to a receiver that is capable of decoding the signal and outputting to all 5 channels.

    C. Dolby Pro Logic (DPL) (and Dolby Surround, DS). This is a 4-channel surround signal that can be sent over analog or digital connections. The 4 channels are right (R), left (L), center (C) and rear (r - two signals Rr and Lr, but it is mono so only counts as one channel). DPL can be encoded and transmitted over stereo cables to a receiver that is capable of decoding the signal and outputting to all 4 channels.

    In Apple TV files DPLII, DPL, DS and stereo are encoded in AAC tracks.

    You can read more about these from the pulldown at Dolby's surround sound web page.

    http://www.dolby.com/resources/tech_library/index.cfm

    2. Hardware

    A. Apple TV. The Apple TV has three means of delivering audio: over the HDMI cable, through its optical port, and through its two channel RCA jacks. While the HDMI and optical port can deliver both digital (DD) and analog (DPL, DPLII, DS, stereo), the RCA jacks can only deliver analog audio.

    B. TVs. Many new TVs have inputs for HDMI and optical cables, as well as analog RCA jacks. However, most only decode Dolby Digital delivered through their ATSC tuners (e.g., over-the-air antenna, satellite or cable connections). They generally are unable to decode DD from other hardware sources, such as an Apple TV or DVD player. In addition, they cannot passthrough DD from a device to a receiver; the TVs can only pass analog audio to the receiver. The exception to this rule is the built-in ATSC tuners that all new TVs have. These connections from a TV to a receiver are HDMI, optical cable or coaxial cable, each of which is capable of delivering digital audio information to the receiver.

    C. Receivers/Amps. Most receivers today have the ability to receive and decode Dolby Digital audio (and DTS digital audio, but which will not be discussed since the ATV2 does not do DTS). The least expensive units have optical and/or coaxial digital audio inputs, often more than one, while the more expensive units have these inputs as well as HDMI inputs. In addition, some of the receivers with HDMI inputs also have HDMI outputs and can be used to control your video as well. These HDMI receivers are able to provide DD 5.1 surround while also passing along video to your TV.

    3. Software

    A. Quicktime Player. With the release of the Apple TV 2 update, Quicktime for the ATV2 saw an update with the ability to passthrough AC-3 Dolby Digital (e.g., 5.1) surround sound, provided the movie file has such a track and that a receiver capable of decoding DD is connected directly to the ATV. This feature of autoselecting audio tracks in ATV's Quicktime apparently is not available for Macs, although Quicktime on Macs can passthrough AC-3 DD if the track is enabled (and with DVDs and DVD Player app).

    B. Handbrake. With the release of version 0.9.2, Handbrake included the ability to encode videos with both AAC (analog) and AC-3 5.1 (digital) surround sound, provided your source DVD has 5.1 surround sound tracks. By choosing the "Apple TV" preset in Handbrake, you get both audio tracks, with the AAC turned "on" and the AC-3 turned "off" by default. (This is also how the high-def with DD movie rentals from Apple are arranged, too.) The new Quicktime that ships with the ATV2 update automatically determines if (1) the movie file has an AC-3 track and (2) if your receiver is capable of decoding AC-3 audio. If both conditions are true, then the ATV will enable the AC-3 track. Otherwise, the ATV will only use the AAC track as the audio source.

    4. Connections

    A. Non-HDMI Receiver. If your receiver does not have HDMI inputs, then your best solution is to connect your Apple TV to your TV by its HDMI cable or component cables, then use a Toslink cable to connect your ATV to your receiver. You cannot connect your Apple TV to your TV with HDMI or optical cable and expect your TV to passthrough DD 5.1 to your receiver. The receiver must be connected directly to the ATV by optical cable. The audio can only be passthroughed once (but video can be passed at least twice). This is because of Digital Rights Management issues. If your TV does not have HDMI and you are using the component video connections from your ATV, then you should also connect your ATV audio to your TV using the RCA audio jacks.

    B. HDMI Receiver. If your receiver has HDMI inputs, connect your ATV to it using an HDMI cable. You then need to connect your receiver's video-out to your TV, either by HDMI, component or composite cables. In this way, you will get DD 5.1 surround sound.

    C. Listening to audio without having your TV on. If you listen to music, audio books or audio podcasts with the ATV, you may not want your TV on while using these media. If your RCA jacks on your ATV are unused, you can connect them to your receiver in such a way that it is unnecessary to leave your TV on while listening to audio media. For my setup, I have our ATV connected to our TV by HDMI, and to our Onkyo receiver by its optical cable. Because the RCA jacks on our ATV were unused, I connected them to the "CD" input on the receiver. With this setup, I set the receiver to CD mode, then start a music playlist from the ATV, then turn off the TV. The music continues to play until the last song.

    See this post for the break in this thread between ATV2 and ATV1.


    *******************************************************
    * The information below is the original post and applies to
    * pre-ATV2 only. If you still use versions 1.0 or 1.1, you should
    * use this information.
    *******************************************************

    OK, I'm going to try to clarify audio on an Apple TV versus a Mac Mini. I hope to be clear and accurate, but your mileage may vary. I'm only going to discuss Dolby Labs' technology, and not DTS. I am no expert, but this is the information I've manage to pull together. If any of this is incorrect, I welcome and appreciate corrections by other forum members. As new information becomes available, I will revise this post.

    1. Definitions

    Dolby Pro Logic (DPL) (and Dolby Surround, DS). This is a 4-channel surround signal that can be sent over analog or digital devices. The 4 channels are right (R), left (L), center (C) and rear (r - two signals Rr and Lr, but it is mono so only counts as one channel). DPL can be encoded and transmitted over stereo (i.e., 2 lines, right and left) cables to a receiver that is capable of decoding the signal and outputting to all 4 channels.

    Dolby Pro Logic II (DPLII). This is a 5-channel surround signal that can be sent over analog or digital devices. The 5 channels are R, L, C, Rr and Lr. DPLII also can be encoded and transmitted over stereo cables to a receiver that is capable of decoding the signal and outputting to all 5 channels.

    Dolby Digital AC-3 (DD). This is usually 6 channels (termed '5.1') that is principally sent over a digital connection, such as a TOSLINK optical cable from the Mac Mini or Apple TV's optical audio port (but is currently nonfunctional on the ATV because of software limitations) to a receiver. The channels for DD are L, R, C, Rr, Lr and the low frequency LFE channel. The LFE is the '.1' channel.

    You can read more about these from the pulldown at Dolby's surround sound web page.

    http://www.dolby.com/resources/tech_library/index.cfm

    2. Hardware

    Apple TV. It has an audio chip that can decode up to a 7.1 signal. It has both optical audio out (which is capable of delivering a DD signal, but currently is not implemented) and RCA stereo jacks (which are analog and can thus deliver DPL or DPLII, but not DD, signals). The Apple TV uses Quicktime to play its video content and encoded AAC audio (which is distinct from AC-3 audio). It does not have DVD Player application that ships will all Macs.

    Mac Mini. I do not know what the audio chip is inside the Intel-based Minis, but it is capable of at least 5.1 audio passthrough using its optical audio-out port (which is also a dual-function analog stereo-out port). If you connect a TOSLINK cable to it you get optical output (DD, DPLII, DPL, DS, Stereo). If you connect a 1/4" stereo to RCA cable to it you get analog (stereo, DPL, DPLII, but not DD) output. The Mac Mini can use Quicktime or DVD Player to play video content, depending on the file type.

    3. Software

    DVD Player. This program on the Mac Mini is capable of sending Dolby Digital AC-3 audio data through the optical port of a Mac Mini via a TOSLINK cable. It cannot send AC-3 out via a stereo-to-RCA cable. If you play a DD 5.1-encoded DVD (real or ripped to your hard drive with MacTheRipper) using DVD Player and you have a TOSLINK cable between your Dolby Digital-capable receiver and Mac Mini, DVD Player will passthrough the AC-3 info to the receiver, which will decode it into all 6 channels (L, R, C, Lr, Rr, LFE). This will give you 5.1 surround sound. If the DVD only has DPL, DPLII or 2-channel stereo, then only those can be passed through. You cannot get 5.1 surround from DPLII, DPL or stereo audio.

    Quicktime Player. The program is found on the Mac Mini as well as the Apple TV. Since it cannot decode AC-3 audio files, there is currently no way to get AC-3 audio (i.e., 5.1 surround) from Apple TV to a 5.1 receiver. Quicktime is capable of encoding 6 discrete audio channels, but they are in AAC, not AC-3. Since there are no consumer receivers on the market that can decode AAC, you cannot get 5.1 surround sound from the Apple TV or Mac Mini using Quicktime. Quicktime will, however, allow the playback of stereo and since DPL and DPLII can be encoded in stereo channels you can get 4-channel (DPL) or 5-channel (DPLII) audio from your Apple TV or Mac Mini, provided they are connected to a receiver capable of decoding DPL or DPLII. (Note, though, that there is usually channel leakage in DPL and DPLII, thus separation is not as good as it is with DD.)

    Handbrake. With the release of version 0.9, Handbrake included the ability to convert DD AC-3 into DPLII 5-channel surround in the transcoded Quicktime video file. If you select the Apple TV preset for a DVD with 5.1 AC-3, Handbrake will convert the 5.1 AC-3 file into a DPLII stereo audio track (see "Track 1 Mix" on attached screen shot) of the H.264 output MPEG4 file and it will contain the L, R, C, Rr, and Lr channels, but not the LFE channel. If you play this on the Apple TV using a TOSLINK cable (or the RCA jacks) to connect the ATV to your DPLII-capable receiver, you will get 5-channel surround (but not 5.1 surround). Handbrake also has a provision to convert the 5.1 AC-3 audio into 6 discrete channels encoded in AAC in Quicktime; however, as mentioned above, since there are no consumer receivers on the market today that can decode AAC from Quicktime audio there's really not much point in using this feature of Quicktime. I have tried this, and it does play on my Onkyo receiver, but it is not 5.1 surround.

    VLC. Handbrake can also be used to transcode DVDs into MKV format containers with H.264 video encoding and Dolby Digital AC-3 5.1 surround sound passthrough (see second attachment). These files will not play in Quicktime, thus cannot be used for playback on the ATV. However, VLC will play them on a Mac and passthrough the AC-3 audio file through the optical port to a receiver using a Toslink cable. (Install Perian for good measure.) Provided your receiver has an optical input and the ability to decode Dolby Digital, you can get 5.1 surround sound with your movies. One word of caution: VLC is very buggy and skipping ahead can cause all kinds of problems with crashing VLC, and also crashing your audio in such a way that the only fix is to reboot your Mac. In addition, these files are typically much larger than MP4 H.264 stereo/DPL/DPLII files because of the size of AC-3. A 2 gig movie with MP4/DPLII will be about 3 gigs as an MKV/AC-3.

    DVD2OneX. DTOX is an app that will take a DVD ripped to your hard drive with MacTheRipper and compress it to a smaller size. One preset is to make it small enough that you can fit it on a single-layer DVD. You can use it to clone the DVD or to make a DVD for individual videos from the DVD. If you have Leopard on your Mac, Front Row will now allow you to play DVDs from your hard drive. Because of this, I have my 5.1 surround sound-intensive DVDs MTR/DTOX'd to 4.2 gig VIDEO_TS folders for playback on my Mac Mini home theater system. Its much cleaner and reliable than playback of MKV files with VLC. I have an external firewire drive with a folder called 'DVD' in which these VIDEO_TS folders are stored, and an alias to the DVD folder is copied to my Home/Movies folder. When Front Row is launched, select Movies, then drive down to the DVD folder of your choice. Of course, these ripped VIDEO_TS folders can also be played by DVD Player with passthrough of the 5.1 surround sound to your receiver, as well.
     

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  2. thread starter macrumors 604

    Cave Man

    #2
    If anyone is looking for a 5.1 home theater surround sound system, the Onkyo HT-SR600 is very inexpensive and provides optical input for the Apple TV or Mac Mini. It only has component video input (no HDMI or DVI), but component is still very good. B&H Photo sells it for $240 and Circuit City currently has it on sale for $270. I've not actually heard this unit, but it is descendent of the Onkyo system I have (HT-S580). It will decode Dolby Digital and DTS (both 5.1), should the ATV (and Quicktime) ever get there. It also does Dolby Pro Logic II (5-channel) and below.
     
  3. macrumors regular

    Joined:
    Dec 11, 2006
    #3
    Nice post, thanks for taking the time to summarize; I own 2 ATVs and have been thinking of converting my dvd collection to h.264, so I'm glad to know that I'll lose discrete surround and the LFE channel if I do so at this point. I see no point in tackling this project at present, as I'm sure if the capability is added in the future any current rips will have to be repeated, and I only want to have to do this once. Thanks again!
     
  4. macrumors 6502

    Joined:
    Sep 3, 2007
    Location:
    130 miles NE of Cupertino
    #4
    Agreed. Unless you retain DD or DTS it's pointless to rip at this time. Hopefully that will be resolved in the near future.

    I started a similar thread a while back discussing the audio output of the ATV here.
     
  5. thread starter macrumors 604

    Cave Man

    #5
    It seems to me that the path of least resistance would be to store the files for ATV as discrete 6-channel AAC audio, then have the ATV convert it to AC-3 or DTS (probably requiring licensing from Dolby and/or DTS) on the fly as it sends it out the optical port. I don't know if the processor is powerful enough to do that and deal with decompression to 720 video (through the GPU) concurrently.

    Certainly, storing AC-3 audio data is not an option. It is simply too big for Apple's model of movie downloads, either for purchase or rental. Put on top of that the video requirements for 720, you're going to have 4 gig files to download for a 2 hour 5.1 movie. I just don't see that happening. AAC is the way to go.

    So, any thoughts on the ATV's ability to decode H.264 and convert AAC to AC-3/DTS in real-time? What about conversion to Neo6 - that should be faster, right?
     
  6. macrumors 6502

    Joined:
    Jan 10, 2007
    #6
  7. macrumors 65816

    saltyzoo

    Joined:
    Oct 4, 2007
    #7
    I apologize for derailing the thread to some degree, but does anybody know of an easy way to connect a mini (toslink) to a receiver with discrete 5.1 RCA inputs (IE: 6 RCA jacks)?
     
  8. macrumors 6502a

    Joined:
    Aug 28, 2007
    #8
    I imagine you'd have to get a converter (if one exists). Your best bet would probably be to check over at AVS.

    Cave Man - Also a thanks for the write up. So even if Apple were to upload the software for the chip to decode 5.1, it wouldn't do any good since the software (Quicktime) would not be able to read the data from the file?
     
  9. thread starter macrumors 604

    Cave Man

    #9
    If it's solely software, then they can add it to Quicktime. The problem is that AC-3 and DTS audio files are very large. This is why AAC is so attractive - it is an efficient compression algorithm. But even then, if you have 6 audio signals, that's a lot of information for a H.264 720p video file (which we're all hoping for) that needs to be downloadable from iTMS. Perhaps most limiting, though, is the lack of recievers that can decode AAC. The only 5.1 capable receivers I know of can decode AC-3 and DTS. There are some on the market that can decode Neo6, which is a highly compressed 6 channel from DTS.

    If you want the smallest files, I think Apple has to do discrete 6-channel AAC in Quicktime and license the compression algorithms from Dolby or DTS to convert the AAC to one of these formats on the fly, then send it out the optical port to your 5.1 receiver for decoding. It's a tough one to call.

    The specs on the chip are here. I'm not a hardware guy, but it seems to me that this chip can support a variety of audio sources and is S/PDIF, so it can do the passthrough of DD or DTS without decoding it since it's just a data file (I presume).
     
  10. macrumors 65816

    Joined:
    Sep 10, 2007
    Location:
    Southern California
    #10
    ok so my question is this. Do most of you have your aTV plugged in via the optical port or the rca jacks? I only have mine via the optical port and it seems to be just fine.
     
  11. macrumors regular

    Joined:
    Feb 10, 2007
    #11
    Great post but....

    I have been looking into this issue since I purchased my Apple TV a few months ago. I must admit I was pretty disappointed the find that it only worked in Stereo but that is really the only issue I have with my Apple TV.

    That said, your post, like many others provides more questions on of which is:

    Q: I encode my DVDs using Handbrake so I assume that the surround signal is there but the Apple TV simply can't play it. Is this correct? I can only assume that it is otherwise why else would Handbrake have the settings for surround sound as shown in the image you've posted.

    Surely the way to test this is to play the file on a Mac Mini or other Mac using the toslink connection.

    If this is correct, then I think the next step would be to boot a hacked Apple TV into Mac 10.4.8 and see if the file can be played through Quicktime player in OS X. Has anyone ever done this? Am I missing a step?

    If this IS possible then surely the issue is a software one.

    If I'm missing something let me know.
    :confused:
     
  12. macrumors 6502

    Joined:
    Jan 10, 2007
    #12
    **sigh**

    Take a look at the link from Roughly Drafted I posted above and I think it'll answer your questions. From the article here is a snippet:

    --RD--
    DTS 5.1 from Apple TV
    In addition to stereo cables, Apple TV also features a Toslink digital optical port. Since we can send raw digital audio data over the Apple TV's optical output, can't we send DTS digitally encoded 5.1 as well?

    Of course we can. Download a DTS sample file in WAV format, drop it into iTunes, and Apple TV will happily sync it and play it. Unlike Pro Logic audio, it will sound like static over regular stereo speakers, but hooked up to a DTS receiver, it is decoded into 5.1 channels of sound and played back in real DTS 5.1 surround.

    The only limitation with DTS 5.1 sound right now is that Apple isn't offering it on its own movie downloads. The Apple TV can certainly “do it,” because it doesn't have to “do” anything; it merely passes it on to the 5.1 DTS decoder that anyone with 5.1 surround speakers already has.
    --RD--

    Time will tell if Apple does anything now or just waits for AAC capable receivers to become more common. In the meantime, also check out the A52Codec and what people are doing with it.
     
  13. macrumors regular

    Joined:
    Feb 10, 2007
    #13
    But it doesn't DO IT!!!

    OK, Call me thick if you want but I'm obviously missing something. I have an Apple TV and a surround sound Amp and like 99% of the population it's not AAC compatible. So I only ever see two speakers on the "little diagram" that usually lights up like a Christmas tree when connected to my DVD player. So I can only conclude that Apple TV is not sending a 5.1 signal that my Amp can decode. Is this correct?

    Q: Will the codec you suggested remedy this?

    Q: Should I just use my Mac Mini and front row instead? I want it simple as I spend all day in front of a computer and the last thing I want to do when I sit down in the evening is "fiddle"

    Q: Why did Apple make this so hard??

    Edit: By the way, I'm using the Optical connections on the Apple TV NOT the analogue.

    Thanks for your advice and suggestions so far.
     
  14. thread starter macrumors 604

    Cave Man

    #14
    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.

    On the DVD its audio is a 5.1 Dolby Digital file. However, it was extracted using Handbrake 0.9.1 with the Apple TV preset. Handbrake converted it to a Dolby Pro Logic II 5-channel (not 5.1-channel) file. This file can be transmitted over stereo R and L RCA cables (or the TOSLINK cable) to your amplifier. If your receiver/amplifier can decode DPLII (check your amp's manual) then you should get 5-channel surround sound by playing this file. I have tried it on my Mac Mini home theater system (Onkyo) using Quicktime and it really, truly is 5-channel surround. When you open the file in Quicktime, choose Window -> Show Movie Properties. On this window, select Sound Track, then Audio Settings. You will see that there are only 2 tracks; right and left. This is the beauty of DPLII - it is a 5-channel signal that can be stored on a 2-channel track. The Mini or ATV simply passes these two tracks to your DPLII-capable receiver/amp, which then decodes all 5 channels and sends them to the correct speakers: L, R, C, Lr, Rr. The only one that's missing is the low frequency (bass) LFE (which is the '.1' track in 5.1). Play it on your ATV or Mini with a DPLII surround sound system and you will hear for yourself that not only is it surround, it is pretty darn good. Only absolute separation of channels and the richness of the LFE are missing.

    The only better (audio) aspect about the Mini is that DVD Player app on the Mini will give you AC-3 5.1 (6-channel, including the low frequency LFE) surround passthrough from your DVD VOB files to your DD/DTS amplifier, while the Quicktime on the Apple TV (or Mini, for that matter) can only give you 5-channel (Dolby Pro Logic II) from your Handbrake-ripped MPEG4 video files (provided you use the ATV preset that converts AC-3 5.1 to DPLII 5-channel).

    Probably for proprietary reasons. Maybe increased file size (download problems from iTMS). No one knows why it's taking Apple so long to get this sorted out. If Dolby doesn't want to license DPLII to Apple, we may never see a solution. Maybe Apple's trying to leverage amplifier/receiver manufacturers to sell units that can decode Quicktime discrete 6-channel AAC. Your guess is as good as anyone's.

    Either should work since the ATV is sending the encoded signal to your receiver, not the decoded signal, but the optical cable is better.
     
  15. macrumors 6502

    Joined:
    Jan 10, 2007
    #15
    You also have a Mac mini? Then like the OP talks about, that sounds like your best bet as you have easier/better ways of passing surround through it (DVDPlayer, VLC, etc.). Trying to do surround sound with the ATV is a kludge. Yeah, good question, why did Apple make it so hard..

    Side Note: It's interesting you have a mini and an ATV as I do as well. My setup consists of the ATV off my main TV, my Sammy LCD in the living room, while my mini is the media server and is connected to my bedroom's old Sony CRT (EyeTV, Frontrow, etc.). Thus is why I'm also very interested where Apple is going with the ATV and surround sound. :)
     
  16. macrumors 6502

    Joined:
    Jan 10, 2007
    #16
    I've often wondered if it's the studios holding them hostage? Would it be that hard to offer a good, better, best version of the movie and make everybody happy and then update the ATV for the HD videos...
     
  17. thread starter macrumors 604

    Cave Man

    #17
    My ATV is through RCA cables. I only have R, L, and C speakers on my old Sony receiver, which is pre-optical cable days. My Mini is connected to my Onkyo receiver for my home theater - a projector-based system with a 10' wide screen. :D

    Optical is the way to go, I would think. Less of an issue of cross-talk that can occur with poorly-insulated copper wires.
     
  18. thread starter macrumors 604

    Cave Man

    #18
    I really don't know. Hardware wise, the limitation are the receivers/amps. They only do DD or DTS for x.1 surround sound. There's also THX, but that's a lot more expensive. Software seems the easiest route to me, but you'd have to convince Dolby, DTS and Apple that everyone can have a slice of the pie.
     
  19. macrumors 6502a

    Joined:
    Aug 28, 2007
    #19
    I thought about this some more last night and I may be tempted to jump in since I can us a lot of stuff I have now (older TV shows) that do not even have a 5.1 track.

    However, based on TuckBodi's post it appears that ATV will support pass-through of DTS 5.1 data so that the receiver can prcoess the signal (over toslink). This is an accurate statement, correct?

    Next question - if you're sending a DPLII signal from the ATV, even if it's 5.0, will the receiver still send a siganl to the sub? I imagine if the frequency was low enough, the sub would kick in even if there was crossover with the normal speakers.

    Lastly - is there any way to transcode a DD signal to DTS? How about the way that that DD+ and DTS-HD are handled in new players? They are both, if I'm not mistaken, automatically downconverted in a DTS stream. Is this a software function or hardware? Perhaps the next version of ATV could use this solution?
     
  20. thread starter macrumors 604

    Cave Man

    #20
    The sub plays, it just doesn't produce the rich sound of a '.1' discrete LFE track. I've played Revenge of the Sith from both the DVD with DVD Player (5.1) and Handbraked H.264 DPLII (5-channel) with Quicktime and the DVD audio is noticeably (but not a whole lot) better than the DPLII. It sounds more spacious (because of absolute channel separation) and the sub really shakes the walls. :D With that said, though, DPLII is a lot better than just 2-track stereo audio. Some surround is better than no surround.

    I can't answer your other two questions, but for the ATV the limitations are the software codecs. With the 1.1 update, Apple broke ssh and AFP, so to put any new codecs on the ATV you'd have to pull the drive out of the ATV and mount it on your Mac, then copy those Intel binary codecs to their proper places, and reassemble your ATV. It's not hard; after all, the ATV is simply OS X. However, Back Row specifically uses Quicktime for its video playback, so any codec would have to be compliant with the Quicktime installed on the ATV. Apple can do this for us with an update. But for whatever reason, they haven't.
     
  21. thread starter macrumors 604

    Cave Man

    #21
    It could be the studios. I don't know how much more (or less) they make off of HD videos (which is what Apple should be providing: 720p in 5.1 surround) sold in brick and mortar shops compared to iTMS. It's also a function of bandwidth. True 5.1 encodes 6 discrete audio channels that can significantly contribute to file size. The nice thing about AAC is it's very efficient - small file size but retaining high-quality sound. But even then, if you stick 6 AAC audio tracks onto a 720p HD video, you're talking some serious file sizes. I bought Ratatouille from the iTMS and it was something like 1.6 gb in size. That's a standard definition, two-channel stereo file of about 1 hour and 50 minutes in length. Make it 720p with 6-channel audio and it's probably going to be around 3 or 4 gigs in size (maybe more). That's almost an overnight download for my DSL bandwidth. I can't imagine how long it would take for a 1080i 5.1 file to download.
     
  22. thread starter macrumors 604

    Cave Man

    #22
    Audio file size comparison

    I extracted the audio from the DVD VOB file used to generated the H.264 file in my previous post, and here are the file sizes of each:

    AC3 = 2.1 mb (6-channel surround)
    AAC = 1.5 mb (6 discrete AAC channel surround)
    DPLII = 628 kb (5-channel surround)

    So, even if Apple could distribute their movies in AAC 5.1 surround, the file sizes would probably still be pretty hefty. Not good for downloads.
     
  23. macrumors 6502a

    cohibadad

    Joined:
    Jul 21, 2007
    #23
    I software hacked my ATV recently and have ssh and AFP without pulling the hard drive. I posted relative links in another thread if anyone is interested. It requires some command lines but wasn't really hard. I have 1.1.

    Also, I downloaded the DTS file linked on the roughlydrafted post and it does play perfectly 5.1 streamed to ATV and displays as DTS. I use HDMI from ATV to my receiver.
     
  24. thread starter macrumors 604

    Cave Man

    #24
    Yes, I'd like to see that link for reestablishing ssh and AFP to a 1.1 ATV.

    Thanks
     
  25. macrumors 6502a

    cohibadad

    Joined:
    Jul 21, 2007
    #25
    sure. here is the link http://forums.macrumors.com/showthread.php?t=384664

    I've been thinking about this 5.1 surround sound question. This is probably obvious to many but it should be possible to H.264 encode a movie with say handbrake then demux the audio and reencode the AC3 or DTS to WAV, combine them in QT and save in a MOV container that should play on :apple:TV, yes? The audio would sound like garbage on the mac unless passed through DTS/dolby decoder software, but if passed through a receiver it should work? I think I will try it with 1 chapter as a test. It would be pretty tedious to do a lot of movies without some automation though.
     

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