AC3 Passthrough

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gingerninja
Posts: 2
Joined: Thu May 10, 2007 11:32 am

AC3 Passthrough

Post by gingerninja »

OK I have just got hold of the lastest version 0.8.5b1 for Mac OS X.

Now everytime I try to use the AC3 passthrough all I get is 2 channel audio and not 5.1.

Whats the deal, this used to work on previous versions ?

Cheers
Craig.
hosed
Posts: 1
Joined: Sat May 19, 2007 10:42 pm

AC3 Passthrough

Post by hosed »

I'm having the same problem. This worked before. I'm going back to the older version until this is fixed.
jbrjake
Veteran User
Posts: 4805
Joined: Wed Dec 13, 2006 1:38 am

Post by jbrjake »

There is absolutely nothing wrong with AC3 pass-through in 0.8.5b1. I just tested to verify. You are obviously setting something incorrectly. Please share all your settings. You need to be using AVI file format with AC-3 Audio selected in the codecs list -- the same as in 0.7.1. Are you seeing "AC3 Passthru" as the Track Mix on the Audio tab?
golias
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Posts: 105
Joined: Wed Jan 03, 2007 7:29 pm

Post by golias »

My biggest beef with AC-3 lately seems to be that there's no perfect way to play it.

I tried adding the AC3 library to quicktime. That plays it, but as a stereo PCM only.

VLC, however, plays AC3 5.1 just fine and dandy... Except there's always about a 3-second delay before the sound kicks on a new file or chapter, or even occasionally after a pause, so I frequently miss some dialog.

Those of you who use AC3 a lot, have you encountered this? If so, what was your work-around?

I would blame it on my amp being slow to understand which kind of signal it is receiving, except I never have this problem with the DVD Player or EyeTV.

Thoughts?
loyalty_anchored
Bright Spark User
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Post by loyalty_anchored »

@golias:

i use ac3 passthrough on my ATV and i find no problems whatsoever with its playback via TOSLINK to my receiver.

the only thing i can complain about is that everytime playback begins there is a very small and short statis POP sound and after that its perfect.

this POP can also occur when i skip to the next chapter, but its so short and its not really that loud, so i live with it.

other then that, tip top!
golias
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Posts: 105
Joined: Wed Jan 03, 2007 7:29 pm

Post by golias »

loyalty_anchored wrote:@golias:

i use ac3 passthrough on my ATV and i find no problems whatsoever with its playback via TOSLINK to my receiver.

the only thing i can complain about is that everytime playback begins there is a very small and short statis POP sound and after that its perfect.

this POP can also occur when i skip to the next chapter, but its so short and its not really that loud, so i live with it.

other then that, tip top!
I'm starting to think that my Sony receiver may be the problem. I've just noticed a delay with EyeTV as well, not when the channel changes, but when the application launches.

I think the receiver is taking a long time to auto-detect the signal the Mac is sending to it. Stereo signals come in right away, but anything with discrete multi-channel sound causes a short wait before the sound kicks in. I was just kind of wondering if other people have run in to a similar problem with AC-3 over S/PDIF. If only there was a way I could get my files to sync up sound first, THEN start playing the video.
TheBum
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Posts: 66
Joined: Tue Apr 10, 2007 12:03 am

Post by TheBum »

golias wrote:I'm starting to think that my Sony receiver may be the problem. I've just noticed a delay with EyeTV as well, not when the channel changes, but when the application launches.

I think the receiver is taking a long time to auto-detect the signal the Mac is sending to it. Stereo signals come in right away, but anything with discrete multi-channel sound causes a short wait before the sound kicks in. I was just kind of wondering if other people have run in to a similar problem with AC-3 over S/PDIF. If only there was a way I could get my files to sync up sound first, THEN start playing the video.
This is similar to an issue experienced by Airport Express users, including myself, before Apple updated the firmware to leave the digital stream on at all times while a computer maintained an AirTunes socket connection: the first few seconds of each track would be chopped off while the receiver (a Pioneer VSX-812K in my case) resync'ed the stream. The only workaround in that case was to enable crossfading with an overlap of a second or so. Short of figuring out some way to prepend a few seconds of audio that would maintain sync when the movie's audio kicked in, I'm not sure there's much you can do.
golias
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Posts: 105
Joined: Wed Jan 03, 2007 7:29 pm

Post by golias »

TheBum wrote:
golias wrote:I'm starting to think that my Sony receiver may be the problem. I've just noticed a delay with EyeTV as well, not when the channel changes, but when the application launches.

I think the receiver is taking a long time to auto-detect the signal the Mac is sending to it. Stereo signals come in right away, but anything with discrete multi-channel sound causes a short wait before the sound kicks in. I was just kind of wondering if other people have run in to a similar problem with AC-3 over S/PDIF. If only there was a way I could get my files to sync up sound first, THEN start playing the video.
This is similar to an issue experienced by Airport Express users, including myself, before Apple updated the firmware to leave the digital stream on at all times while a computer maintained an AirTunes socket connection: the first few seconds of each track would be chopped off while the receiver (a Pioneer VSX-812K in my case) resync'ed the stream. The only workaround in that case was to enable crossfading with an overlap of a second or so. Short of figuring out some way to prepend a few seconds of audio that would maintain sync when the movie's audio kicked in, I'm not sure there's much you can do.
So, what it sounds like you're saying is, I need a media app which turns on the digital stream for a file BEFORE I start to play the file, and keeps it on when I pause.

That, or use an Airport Express, even though the Mac is right next to the amplifier.

If it makes sense for Airport users, why would they not also include this feature in the sound out port of the Mac itself??? :(
Randy_84dger
Posts: 1
Joined: Sat May 26, 2007 10:20 am

Post by Randy_84dger »

I am having the same trouble as the top of this post. Ripping using both Mac and XP, the resulting files contain the AC3 passthru (test.avi ripped on Mac using Version 0.8.5b1 (2007042301)):

Code: Select all

mac84dger:~/Movies al$ mplayer test.avi 
MPlayer dev-CVS-060307-04:23-4.0.1 (C) 2000-2006 MPlayer Team
Mac OSX static build for ffmpegX
CPU: Intel  (Family: 6, Stepping: 6)
FIXME:Hardenabling SSE and SSE2 without detection
CPUflags:  MMX: 1 MMX2: 1 3DNow: 0 3DNow2: 0 SSE: 1 SSE2: 1
Compiled for x86 CPU with extensions: MMX MMX2 SSE SSE2

Playing test.avi.
AVI file format detected.
VIDEO:  [XVID]  704x400  24bpp  25.000 fps  1054.7 kbps (128.7 kbyte/s)
==========================================================================
Opening audio decoder: [liba52] AC3 decoding with liba52
Using SSE optimized IMDCT transform
AC3: 5.1 (3f+2r+lfe)  48000 Hz  448.0 kbit/s
Using MMX optimized resampler
AUDIO: 48000 Hz, 2 ch, s16le, 448.0 kbit/29.17% (ratio: 56000->192000)
Selected audio codec: [a52] afm: liba52 (AC3-liba52)
==========================================================================
but the 'file' command reports:

Code: Select all

mac84dger:~/Movies al$ file test.avi 
test.avi: RIFF (little-endian) data, AVI, 704 x 400, 25.00 fps, video: XviD, audio: Dolby AC3 (stereo, 48000 Hz)
I wouldn't have noticed it if hadn't been for the script i use for tagging avis with [DivX/XviD Mp3/AC3 mono/stereo/5.1], which uses 'file' :? Do i need to re-write the script or is something not being written correctly in the file info? :D

Cheers,
Al.
gbooker
Posts: 43
Joined: Sat Apr 07, 2007 8:38 pm

Post by gbooker »

First of all, AVI sucks. It should never have been used to contain multi-channel audio, nor video with B frames, nor MP3, nor anything else that people here are doing with it. There now that is done, I'll tell you why mplayer gets it right but file gets it wrong:

AVI has absolutely no concept of a .1 channel, and furthermore, knows jack about channel layout. The best way to properly mark a 5.1 channel audio track in an AVI is to mark it as 6 channel. Apparently, HB is lying and marking it as 2 channel (which is actually quite common. 5 channel is also common). File simply looks at how many channels the AVI file thinks the track has. Mplayer is looking at the AC3 sample data (obvious by the fact that it knows the channel layout as well).

This is why Perian 1.0 will ignore the channel count provided by the AVI file and instead look at the sample data for AC3.
po23
Posts: 8
Joined: Sun May 27, 2007 11:31 pm

Post by po23 »

But which one is "right"? Is the AC3 that is inside the file 5.1 or 2? I guess I'm confused as to whether it is a labelling problem or something "real".
hawkman
Veteran User
Posts: 609
Joined: Sat Feb 17, 2007 9:46 pm

Post by hawkman »

By the sound of things, it's 5.1, but you can't tell from the container because it can't handle the idea of 5.1 - so it has to be lied to when it's made, and it in turn lies to you. You'd have to look at the actual data to know that it's 5.1.
po23
Posts: 8
Joined: Sun May 27, 2007 11:31 pm

Post by po23 »

Ah that makes sense. Thanks.
golias
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Posts: 105
Joined: Wed Jan 03, 2007 7:29 pm

Post by golias »

golias wrote:
TheBum wrote:
golias wrote:I'm starting to think that my Sony receiver may be the problem. I've just noticed a delay with EyeTV as well, not when the channel changes, but when the application launches.

I think the receiver is taking a long time to auto-detect the signal the Mac is sending to it. Stereo signals come in right away, but anything with discrete multi-channel sound causes a short wait before the sound kicks in. I was just kind of wondering if other people have run in to a similar problem with AC-3 over S/PDIF. If only there was a way I could get my files to sync up sound first, THEN start playing the video.
This is similar to an issue experienced by Airport Express users, including myself, before Apple updated the firmware to leave the digital stream on at all times while a computer maintained an AirTunes socket connection: the first few seconds of each track would be chopped off while the receiver (a Pioneer VSX-812K in my case) resync'ed the stream. The only workaround in that case was to enable crossfading with an overlap of a second or so. Short of figuring out some way to prepend a few seconds of audio that would maintain sync when the movie's audio kicked in, I'm not sure there's much you can do.
So, what it sounds like you're saying is, I need a media app which turns on the digital stream for a file BEFORE I start to play the file, and keeps it on when I pause.

That, or use an Airport Express, even though the Mac is right next to the amplifier.

If it makes sense for Airport users, why would they not also include this feature in the sound out port of the Mac itself??? :(
Can anybody else suggest a work-around for this issue? I can't be the ONLY person in the world who is having a problem connecting their Mac to an amp via S/PDIF and losing the first few seconds of the signal, can I?

I am at my wit's end here. :?
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