Strange AC3 mkv sync issues

[MarkyMarky]

I have problems playing some HD mkv movies thru USB on my TV (sound dropuot every few seconds). The movies play fine on the PC. I successfully fixed this issue in one mkv file by extracting audio track using MKVextractGUI2, reencoding AC3 track using BeHappy (Aften AC3 CBR @ 448kbps profile), stretching it along the reencoding process to the video track size and then muxing it using mkvmerge.
I tried similar process with another mkv file with TV sound issue. Its audio track is AC3 CBR 384 Kbps, 6 channels, 48 KHz, 16bit. When I demux it to separate AC3 file using MKVextractGui2, duration of the track is 5914208ms, duration of the videotrack is 6134957ms. Then I reencode it as described above to fit movie duration and mux it to the movie. When I play the movie, sound is in sinc in the very beginning and in the very end. Along the movie it's out of the sync. In some parts the sound is before video in others vice versa. What the heck?

(I tried another approach too. I muxed extracted audio track (not the reencoded one) back to the video using mkvmerge. Without any audio stretching parameters in mkvmerge audio ends before video (logical, as its lenght is shorter). So I set audio stretching option in mkvmerge to fit video size. And guess what, resulting movie has similar sync issue, begginnig and end is fine, in the middle out of sync. Any ideas?)

I'm quite newbie to this, maybe I'm missing something obvious...

[guns1inger]

My guess is that the overall bitrate is too high for your TV to either process smoothly, or to load form the USB. In the first case, just lowering the bitrate of the audio appears to have been enough, however if the audio is already encoded with a low bitrate - and 384 kbps is relatively low for HD - then encoding it at a higher bitrate won't solve your problem.

You are also doing something very wrong if you are having to stretch the audio after simply demuxing. If the audio played in sync before demuxing, demuxing should not have caused such large run time discrepancies.

Can I suggest a simpler process ? Download Xvid4PSP 5.37, load up your MKV file, keep video to Copy and re-encode your audio only (if that is what you want to do), selecting MKV as the output container. The process should only take a few minutes, and you shouldn't have any of these hassles.

It may also be worthwhile posting a mediainfo of the problem file before you screw with it.

[MarkyMarky]

In both cases I reencoded from lower to higher bitrate. So bitrate has nothing to do with it. I was able to play movies with higher bitrates via same USB device. First movie that worked after encoding has slower bitrate (384) before encoding and higher (448) after encoding.
As for shorter duration of the audio stream after demuxing - my guess is that this audio stream (in my native language) someone custom-added to the movie and was not originally part of it. My explanation to dropouts when playing on the TV is, that shorter audio stream was stretched along muxing process by adding "empty space" (my laic interpretation). This "empty space" is handled correctly by the PC, but causes TV drop out once in few seconds. Looks like tv cannot handle smoothly distributed "empty space" and "plays it" as whole every few seconds and this is hearable as about half second drop out. This theory I verified with first movie in which I reencoded audio stream to have same duration as video so no "empty space" had to be added during muxing to stretch the audio stream. This same works with second movie, there are no sound dropouts during playback, but theres out of sync issue I cannot understand.
Also remember when I do no reencoding with demuxed stream and simply mux it back to the movie with stretch option in mkvmerge, dropouts remain and in addition there are sync issues. So reencoding is not the problem here.

I tried xvid4psp as you suggested with no success. First used "copy" method for both audio and video streams. Then tried "copy" method for video and reencoded audio to AC3 448kbps. In both cases audio was faster than video and ended sooner leaving rest of movie silent.

[MarkyMarky]

Here's media info of original movie with problematic audio stream Audio #1 (Audio #2 works ok):
General
Count : 270
Count of stream of this kind : 1
Kind of stream : General
Kind of stream : General
Stream identifier : 0
Unique ID : 215526122828217629614608937766516579299
Unique ID : 215526122828217629614608937766516579299 (0xA224D245A61023EBB8210CC5F1825BE3)
Count of video streams : 1
Count of audio streams : 2
Count of text streams : 2
Video_Format_List : AVC
Video_Format_WithHint_List : AVC
Codecs Video : AVC
Video_Language_List : English
Audio_Format_List : AC-3 / DTS
Audio_Format_WithHint_List : AC-3 / DTS
Audio codecs : AC3 / DTS
Audio_Language_List : Czech / English
Text_Format_List : UTF-8 / UTF-8
Text_Format_WithHint_List : UTF-8 / UTF-8
Text codecs : UTF-8 / UTF-8
Text_Language_List : Czech / Czech
Complete name :movie.mkv
Folder name :
File name : movie
File extension : mkv
Format : Matroska
Format : Matroska
Format/Url : http://packs.matroska.org/
Format/Extensions usually used : mkv mka mks
Commercial name : Matroska
Codec : Matroska
Codec : Matroska
Codec/Url : http://packs.matroska.org/
Codec/Extensions usually used : mkv mka mks
File size : 9632030148
File size : 8.97 GiB
File size : 9 GiB
File size : 9.0 GiB
File size : 8.97 GiB
File size : 8.971 GiB
Duration : 6134957
Duration : 1h 42mn
Duration : 1h 42mn 14s 957ms
Duration : 1h 42mn
Duration : 01:42:14.957
Overall bit rate : 12560192
Overall bit rate : 12.6 Mbps
Stream size : 191663488
Stream size : 183 MiB (2%)
Stream size : 183 MiB
Stream size : 183 MiB
Stream size : 183 MiB
Stream size : 182.8 MiB
Stream size : 183 MiB (2%)
Proportion of this stream : 0.01990
Encoded date : UTC 2008-11-10 09:40:31
File creation date : UTC 2011-01-03 16:17:50.229
File creation date (local) : 2011-01-03 17:17:50.229
File last modification date : UTC 2008-11-10 09:49:48.984
File last modification date (loc : 2008-11-10 10:49:48.984
Writing application : mkvmerge v2.2.0 ('Turn It On Again') built on Mar 4 2008 12:58:26
Writing library : libebml v0.7.7 + libmatroska v0.8.1
Writing library : libebml v0.7.7 + libmatroska v0.8.1

Video
Count : 192
Count of stream of this kind : 1
Kind of stream : Video
Kind of stream : Video
Stream identifier : 0
ID : 1
ID : 1
Unique ID : 1
Format : AVC
Format/Info : Advanced Video Codec
Format/Url : http://developers.videolan.org/x264.html
Commercial name : AVC
Format profile : High@L4.1
Format settings : CABAC / 5 Ref Frames
Format settings, CABAC : Yes
Format settings, CABAC : Yes
Format settings, ReFrames : 5
Format settings, ReFrames : 5 frames
Internet media type : video/H264
Codec ID : V_MPEG4/ISO/AVC
Codec ID/Url : http://ffdshow-tryout.sourceforge.net/
Codec : V_MPEG4/ISO/AVC
Codec : AVC
Codec/Family : AVC
Codec/Info : Advanced Video Codec
Codec/Url : http://ffdshow-tryout.sourceforge.net/
Codec profile : High@L4.1
Codec settings : CABAC / 5 Ref Frames
Codec settings, CABAC : Yes
Codec_Settings_RefFrames : 5
Duration : 6134968
Duration : 1h 42mn
Duration : 1h 42mn 14s 968ms
Duration : 1h 42mn
Duration : 01:42:14.968
Bit rate : 10676000
Bit rate : 10.7 Mbps
Width : 1920
Width : 1 920 pixels
Height : 800
Height : 800 pixels
Pixel aspect ratio : 1.000
Display aspect ratio : 2.400
Display aspect ratio : 2.40:1
Frame rate : 23.976
Frame rate : 23.976 fps
Frame count : 147092
Resolution : 8
Resolution : 8 bits
Colorimetry : 4:2:0
Color space : YUV
Chroma subsampling : 4:2:0
Bit depth : 8
Bit depth : 8 bits
Scan type : Progressive
Scan type : Progressive
Interlacement : PPF
Interlacement : Progressive
Bits/(Pixel*Frame) : 0.290
Delay : 0
Delay : 00:00:00.000
Delay, origin : Container
Delay, origin : Container
Stream size : 7988107308
Stream size : 7.44 GiB (83%)
Stream size : 7 GiB
Stream size : 7.4 GiB
Stream size : 7.44 GiB
Stream size : 7.440 GiB
Stream size : 7.44 GiB (83%)
Proportion of this stream : 0.82933
Writing library : x264 - core 65 r999 cc51047
Writing library : x264 core 65 r999 cc51047
Writing library/Name : x264
Writing library/Version : core 65 r999 cc51047
Encoding settings : cabac=1 / ref=5 / deblock=1:0:0 / analyse=0x3:0x113 / me=umh / subme=7 / psy_rd=1.0:0.0 / mixed_ref=1 / me_range=16 / chroma_me=1 / trellis=1 / 8x8dct=1 / cqm=0 / deadzone=21,11 / chroma_qp_offset=-2 / threads=12 / nr=0 / decimate=1 / mbaff=0 / bframes=3 / b_pyramid=1 / b_adapt=1 / b_bias=0 / direct=3 / wpredb=1 / keyint=250 / keyint_min=25 / scenecut=40(pre) / rc=2pass / bitrate=10676 / ratetol=1.0 / qcomp=0.60 / qpmin=10 / qpmax=51 / qpstep=4 / cplxblur=20.0 / qblur=0.5 / ip_ratio=1.40 / pb_ratio=1.30 / aq=1:1.00
Language : en
Language : English
Language : English
Language : en
Language : eng
Language : en

Audio #1
Count : 173
Count of stream of this kind : 2
Kind of stream : Audio
Kind of stream : Audio
Stream identifier : 0
Stream identifier : 1
ID : 2
ID : 2
Unique ID : 1547904672
Format : AC-3
Format/Info : Audio Coding 3
Commercial name : AC-3
Mode extension : CM (complete main)
Codec ID : A_AC3
Codec : AC3
Codec : AC3
Codec/Family : AC3
Codec/Info : Dolby AC3
Duration : 6134957
Duration : 1h 42mn
Duration : 1h 42mn 14s 957ms
Duration : 1h 42mn
Duration : 01:42:14.957
Bit rate mode : CBR
Bit rate mode : Constant
Bit rate : 384000
Bit rate : 384 Kbps
Channel(s) : 6
Channel(s) : 6 channels
Channel positions : Front: L C R, Side: L R, LFE
Channel positions : 3/2/0.1
Sampling rate : 48000
Sampling rate : 48.0 KHz
Samples count : 294477936
Resolution : 16
Resolution : 16 bits
Bit depth : 16
Bit depth : 16 bits
Compression mode : Lossy
Compression mode : Lossy
Delay : 0
Delay : 00:00:00.000
Delay, origin : Container
Delay, origin : Container
Delay relative to video : 0
Video0 delay : 0
Stream size : 294477936
Stream size : 281 MiB (3%)
Stream size : 281 MiB
Stream size : 281 MiB
Stream size : 281 MiB
Stream size : 280.8 MiB
Stream size : 281 MiB (3%)
Proportion of this stream : 0.03057
Language : cs
Language : Czech
Language : Czech
Language : cs
Language : ces
Language : cs
dialnorm : -30
dialnorm/String : -30 dB
compr : 5.46
compr/String : 5.46 dB
bsid : 8
dialnorm_Average : -30
dialnorm_Average/String : -30 dB
dialnorm_Minimum : -30
dialnorm_Minimum/String : -30 dB
dialnorm_Maximum : -30
dialnorm_Maximum/String : -30 dB
dialnorm_Count : 2
compr_Average : 5.46
compr_Average/String : 5.46 dB
compr_Minimum : 5.46
compr_Minimum/String : 5.46 dB
compr_Maximum : 5.46
compr_Maximum/String : 5.46 dB
compr_Count : 2

Audio #2
Count : 154
Count of stream of this kind : 2
Kind of stream : Audio
Kind of stream : Audio
Stream identifier : 1
Stream identifier : 2
ID : 3
ID : 3
Unique ID : 71794582
Format : DTS
Format/Info : Digital Theater Systems
Commercial name : DTS
Codec ID : A_DTS
Codec : DTS
Codec : DTS
Codec/Family : DTS
Duration : 6134957
Duration : 1h 42mn
Duration : 1h 42mn 14s 957ms
Duration : 1h 42mn
Duration : 01:42:14.957
Bit rate mode : CBR
Bit rate mode : Constant
Bit rate : 1509750
Bit rate : 1 510 Kbps
Channel(s) : 6
Channel(s) : 6 channels
Channel positions : Front: L C R, Side: L R, LFE
Channel positions : 3/2/0.1
Sampling rate : 48000
Sampling rate : 48.0 KHz
Samples count : 294477936
Resolution : 24
Resolution : 24 bits
Bit depth : 24
Bit depth : 24 bits
Compression mode : Lossy
Compression mode : Lossy
Delay : 0
Delay : 00:00:00.000
Delay, origin : Container
Delay, origin : Container
Delay relative to video : 0
Video0 delay : 0
Stream size : 1157781416
Stream size : 1.08 GiB (12%)
Stream size : 1 GiB
Stream size : 1.1 GiB
Stream size : 1.08 GiB
Stream size : 1.078 GiB
Stream size : 1.08 GiB (12%)
Proportion of this stream : 0.12020
Language : en
Language : English
Language : English
Language : en
Language : eng
Language : en

[MarkyMarky]

Here's media info of the AC3 stream after demuxing:
Audio
Count : 173
Count of stream of this kind : 1
Kind of stream : Audio
Kind of stream : Audio
Stream identifier : 0
Format : AC-3
Format/Info : Audio Coding 3
Commercial name : AC-3
Mode extension : CM (complete main)
Codec : AC3
Codec : AC3
Duration : 5914208
Duration : 1h 38mn
Duration : 1h 38mn 34s 208ms
Duration : 1h 38mn
Duration : 01:38:34.208
Bit rate mode : CBR
Bit rate mode : Constant
Bit rate : 384000
Bit rate : 384 Kbps
Channel(s) : 6
Channel(s) : 6 channels
Channel positions : Front: L C R, Side: L R, LFE
Channel positions : 3/2/0.1
Sampling rate : 48000
Sampling rate : 48.0 KHz
Samples count : 283881984
Frame count : 184819
Resolution : 16
Resolution : 16 bits
Bit depth : 16
Bit depth : 16 bits
Compression mode : Lossy
Compression mode : Lossy
Stream size : 283881984
Stream size : 271 MiB (100%)
Stream size : 271 MiB
Stream size : 271 MiB
Stream size : 271 MiB
Stream size : 270.7 MiB
Stream size : 271 MiB (100%)
Proportion of this stream : 1.00000
dialnorm : -30
dialnorm/String : -30 dB
compr : 5.46
compr/String : 5.46 dB
bsid : 8
dialnorm_Average : -30
dialnorm_Average/String : -30 dB
dialnorm_Minimum : -30
dialnorm_Minimum/String : -30 dB
dialnorm_Maximum : -30
dialnorm_Maximum/String : -30 dB
dialnorm_Count : 32
compr_Average : 5.73
compr_Average/String : 5.73 dB
compr_Minimum : 5.46
compr_Minimum/String : 5.46 dB
compr_Maximum : 5.74
compr_Maximum/String : 5.74 dB
compr_Count : 32

[MarkyMarky]

Here's media info of the AC3 stream after reencoding:
Audio
Count : 164
Count of stream of this kind : 1
Kind of stream : Audio
Kind of stream : Audio
Stream identifier : 0
Format : AC-3
Format/Info : Audio Coding 3
Commercial name : AC-3
Mode extension : CM (complete main)
Codec : AC3
Codec : AC3
Duration : 6134976
Duration : 1h 42mn
Duration : 1h 42mn 14s 976ms
Duration : 1h 42mn
Duration : 01:42:14.976
Bit rate mode : CBR
Bit rate mode : Constant
Bit rate : 448000
Bit rate : 448 Kbps
Channel(s) : 6
Channel(s) : 6 channels
Channel positions : Front: L C R, Side: L R, LFE
Channel positions : 3/2/0.1
Sampling rate : 48000
Sampling rate : 48.0 KHz
Samples count : 294478848
Frame count : 191718
Resolution : 16
Resolution : 16 bits
Bit depth : 16
Bit depth : 16 bits
Compression mode : Lossy
Compression mode : Lossy
Stream size : 343558656
Stream size : 328 MiB (100%)
Stream size : 328 MiB
Stream size : 328 MiB
Stream size : 328 MiB
Stream size : 327.6 MiB
Stream size : 328 MiB (100%)
Proportion of this stream : 1.00000
dialnorm : -31
dialnorm/String : -31 dB
bsid : 8
dialnorm_Average : -31
dialnorm_Average/String : -31 dB
dialnorm_Minimum : -31
dialnorm_Minimum/String : -31 dB
dialnorm_Maximum : -31
dialnorm_Maximum/String : -31 dB
dialnorm_Count : 32

[MarkyMarky]

Finally movie after muxing reencoded stream back:
General
Count : 270
Count of stream of this kind : 1
Kind of stream : General
Kind of stream : General
Stream identifier : 0
Unique ID : 207110848612135334496200149260253583138
Unique ID : 207110848612135334496200149260253583138 (0x9BD0193846B37CD78C593E0864F8D722)
Count of video streams : 1
Count of audio streams : 1
Video_Format_List : AVC
Video_Format_WithHint_List : AVC
Codecs Video : AVC
Video_Language_List : English
Audio_Format_List : AC-3
Audio_Format_WithHint_List : AC-3
Audio codecs : AC3
Audio_Language_List : Czech
Complete name : movie2.mkv
Folder name :
File name : movie2
File extension : mkv
Format : Matroska
Format : Matroska
Format/Url : http://packs.matroska.org/
Format/Extensions usually used : mkv mka mks
Commercial name : Matroska
Codec : Matroska
Codec : Matroska
Codec/Url : http://packs.matroska.org/
Codec/Extensions usually used : mkv mka mks
File size : 8531451080
File size : 7.95 GiB
File size : 8 GiB
File size : 7.9 GiB
File size : 7.95 GiB
File size : 7.946 GiB
Duration : 6134976
Duration : 1h 42mn
Duration : 1h 42mn 14s 976ms
Duration : 1h 42mn
Duration : 01:42:14.976
Overall bit rate : 11125000
Overall bit rate : 11.1 Mbps
Stream size : 169786411
Stream size : 162 MiB (2%)
Stream size : 162 MiB
Stream size : 162 MiB
Stream size : 162 MiB
Stream size : 161.9 MiB
Stream size : 162 MiB (2%)
Proportion of this stream : 0.01990
Encoded date : UTC 2011-01-06 14:24:26
File creation date : UTC 2011-01-06 14:24:26.481
File creation date (local) : 2011-01-06 15:24:26.481
File last modification date : UTC 2011-01-06 14:27:27.578
File last modification date (loc : 2011-01-06 15:27:27.578
Writing application : mkvmerge v4.4.0 ('Die Wiederkehr') built on Oct 31 2010 21:52:48
Writing library : libebml v1.0.0 + libmatroska v1.0.0
Writing library : libebml v1.0.0 + libmatroska v1.0.0

Video
Count : 192
Count of stream of this kind : 1
Kind of stream : Video
Kind of stream : Video
Stream identifier : 0
ID : 1
ID : 1
Unique ID : 1
Format : AVC
Format/Info : Advanced Video Codec
Format/Url : http://developers.videolan.org/x264.html
Commercial name : AVC
Format profile : High@L4.1
Format settings : CABAC / 5 Ref Frames
Format settings, CABAC : Yes
Format settings, CABAC : Yes
Format settings, ReFrames : 5
Format settings, ReFrames : 5 frames
Internet media type : video/H264
Muxing mode : Header stripping
Codec ID : V_MPEG4/ISO/AVC
Codec ID/Url : http://ffdshow-tryout.sourceforge.net/
Codec : V_MPEG4/ISO/AVC
Codec : AVC
Codec/Family : AVC
Codec/Info : Advanced Video Codec
Codec/Url : http://ffdshow-tryout.sourceforge.net/
Codec profile : High@L4.1
Codec settings : CABAC / 5 Ref Frames
Codec settings, CABAC : Yes
Codec_Settings_RefFrames : 5
Duration : 6134968
Duration : 1h 42mn
Duration : 1h 42mn 14s 968ms
Duration : 1h 42mn
Duration : 01:42:14.968
Bit rate : 10676000
Bit rate : 10.7 Mbps
Width : 1920
Width : 1 920 pixels
Height : 800
Height : 800 pixels
Pixel aspect ratio : 1.000
Display aspect ratio : 2.400
Display aspect ratio : 2.40:1
Frame rate : 23.976
Frame rate : 23.976 fps
Frame count : 147092
Resolution : 8
Resolution : 8 bits
Colorimetry : 4:2:0
Color space : YUV
Chroma subsampling : 4:2:0
Bit depth : 8
Bit depth : 8 bits
Scan type : Progressive
Scan type : Progressive
Interlacement : PPF
Interlacement : Progressive
Bits/(Pixel*Frame) : 0.290
Delay : 0
Delay : 00:00:00.000
Delay, origin : Container
Delay, origin : Container
Stream size : 8018106013
Stream size : 7.47 GiB (94%)
Stream size : 7 GiB
Stream size : 7.5 GiB
Stream size : 7.47 GiB
Stream size : 7.467 GiB
Stream size : 7.47 GiB (94%)
Proportion of this stream : 0.93983
Writing library : x264 - core 65 r999 cc51047
Writing library : x264 core 65 r999 cc51047
Writing library/Name : x264
Writing library/Version : core 65 r999 cc51047
Encoding settings : cabac=1 / ref=5 / deblock=1:0:0 / analyse=0x3:0x113 / me=umh / subme=7 / psy_rd=1.0:0.0 / mixed_ref=1 / me_range=16 / chroma_me=1 / trellis=1 / 8x8dct=1 / cqm=0 / deadzone=21,11 / chroma_qp_offset=-2 / threads=12 / nr=0 / decimate=1 / mbaff=0 / bframes=3 / b_pyramid=1 / b_adapt=1 / b_bias=0 / direct=3 / wpredb=1 / keyint=250 / keyint_min=25 / scenecut=40(pre) / rc=2pass / bitrate=10676 / ratetol=1.0 / qcomp=0.60 / qpmin=10 / qpmax=51 / qpstep=4 / cplxblur=20.0 / qblur=0.5 / ip_ratio=1.40 / pb_ratio=1.30 / aq=1:1.00
Language : en
Language : English
Language : English
Language : en
Language : eng
Language : en

Audio
Count : 164
Count of stream of this kind : 1
Kind of stream : Audio
Kind of stream : Audio
Stream identifier : 0
ID : 2
ID : 2
Unique ID : 1981684666
Format : AC-3
Format/Info : Audio Coding 3
Commercial name : AC-3
Mode extension : CM (complete main)
Muxing mode : Header stripping
Codec ID : A_AC3
Codec : AC3
Codec : AC3
Codec/Family : AC3
Codec/Info : Dolby AC3
Duration : 6134976
Duration : 1h 42mn
Duration : 1h 42mn 14s 976ms
Duration : 1h 42mn
Duration : 01:42:14.976
Bit rate mode : CBR
Bit rate mode : Constant
Bit rate : 448000
Bit rate : 448 Kbps
Channel(s) : 6
Channel(s) : 6 channels
Channel positions : Front: L C R, Side: L R, LFE
Channel positions : 3/2/0.1
Sampling rate : 48000
Sampling rate : 48.0 KHz
Samples count : 294478848
Resolution : 16
Resolution : 16 bits
Bit depth : 16
Bit depth : 16 bits
Compression mode : Lossy
Compression mode : Lossy
Delay : 0
Delay : 00:00:00.000
Delay, origin : Container
Delay, origin : Container
Delay relative to video : 0
Video0 delay : 0
Stream size : 343558656
Stream size : 328 MiB (4%)
Stream size : 328 MiB
Stream size : 328 MiB
Stream size : 328 MiB
Stream size : 327.6 MiB
Stream size : 328 MiB (4%)
Proportion of this stream : 0.04027
Language : cs
Language : Czech
Language : Czech
Language : cs
Language : ces
Language : cs
dialnorm : -31
dialnorm/String : -31 dB
bsid : 8
dialnorm_Average : -31
dialnorm_Average/String : -31 dB
dialnorm_Minimum : -31
dialnorm_Minimum/String : -31 dB
dialnorm_Maximum : -31
dialnorm_Maximum/String : -31 dB
dialnorm_Count : 2