Thread: Playback is at half speed after transcoding

Hi,

I'm having an issue with transcoding video correctly. I'm recording OTA ATSC, which is broadcast at 1080i. If I view this live, or view it recorded with no transcoding, it plays back perfectly.

However, when I transcode it (I've tried both mpeg4 and rtjpeg) and play it back, it plays back at what looks like half speed. The audio and video are in sync, but both are running at half speed. When I turn on the OSD, the seconds counter of the current position is also running at half speed, ie it is in sync with how the video looks.

Any idea what is going wrong, and how to fix it? I have two frontends: one connected to an hdtv playing through vdpau, and one connected to an sdtv playing through software. I have to transcode shows to watch them on the sdtv because that frontend is too slow to decode the full bitrate of the broadcast TV.

Thanks in advance!

Here is the backend log file of one of the incorrect transcodings:

Code:

2010-07-14 23:13:24.264 JobQueue: Transcode Starting for So You Think You Can Dance: Autodetect (12.7 GB)
2010-07-14 23:13:24.267 transcode: Transcode Starting: So You Think You Can Dance: Autodetect (12.7 GB)
2010-07-14 23:13:24.307 ProgramInfo(): Updated pathname '':'' -> '1071_20100714185800.mpg'
2010-07-14 23:13:24.523 Using runtime prefix = /usr
2010-07-14 23:13:24.524 Using configuration directory = /home/mythtv/.mythtv
2010-07-14 23:13:24.525 DBPassword is not set in mysql.txt
2010-07-14 23:13:24.554 Empty LocalHostName.
2010-07-14 23:13:24.554 Using localhost value of server
2010-07-14 23:13:24.566 New DB connection, total: 1
2010-07-14 23:13:24.569 Connected to database 'mythconverg' at host: localhost
2010-07-14 23:13:24.576 Closing DB connection named 'DBManager0'
2010-07-14 23:13:24.577 Connected to database 'mythconverg' at host: localhost
2010-07-14 23:13:24.579 Enabled verbose msgs: important
2010-07-14 23:13:24.581 ProgramInfo(): Updated pathname '':'' -> '1071_20100714185800.mpg'
2010-07-14 23:13:24.625 Transcoding from /var/lib/mythtv/recordings/1071_20100714185800.mpg to /var/lib/mythtv/recordings/1071_20100714185800.mpg.tmp
2010-07-14 23:13:24.687 AFD: Opened codec 0xaff03db0, id(MPEG2VIDEO) type(Video)
2010-07-14 23:13:24.688 AFD: codec AC3 has 2 channels
2010-07-14 23:13:24.688 AFD: Opened codec 0xaff04680, id(AC3) type(Audio)
2010-07-14 23:13:24.718 New DB connection, total: 2
2010-07-14 23:13:24.719 Connected to database 'mythconverg' at host: localhost
2010-07-14 23:13:24.726 MythContext: Connecting to backend server: 192.168.0.1:6543 (try 1 of 1)
2010-07-14 23:13:24.733 Using protocol version 56
2010-07-14 23:13:24.733 MainServer::ANN Monitor
2010-07-14 23:13:24.734 adding: server as a client (events: 0)
2010-07-14 23:13:24.735 MainServer::ANN Monitor
2010-07-14 23:13:24.735 adding: server as a client (events: 1)
2010-07-14 23:13:24.738 ProgramInfo(): Updated pathname '':'' -> '1071_20100714185800.mpg'
2010-07-14 23:13:24.761 Transcode: Looking for autodetect profile: Autodetect from 720p
2010-07-14 23:13:24.782 New DB connection, total: 3
2010-07-14 23:13:24.784 Connected to database 'mythconverg' at host: localhost
2010-07-14 23:13:24.877 SampleRate: Attempted to add a rate 32000 Hz, which is not in the list of allowed rates.
2010-07-14 23:13:24.886 Transcode: Using autodetect profile: MPEG2
2010-07-14 23:13:25.016 Copying Audio while transcoding Video
2010-07-14 23:14:31.205 MainServer::ANN Monitor
2010-07-14 23:14:31.205 adding: server as a client (events: 2)
2010-07-14 23:14:31.222 MainServer::ANN Monitor
2010-07-14 23:14:31.229 adding: server as a client (events: 2)
2010-07-14 23:14:31.230 ProgramInfo(): Updated pathname '':'' -> '1071_20100714185800.mpg'
2010-07-14 23:14:31.570 ProgramInfo(): Updated pathname '':'' -> '1071_20100714185800.mpg'
2010-07-14 23:14:31.881 ProgramInfo(): Updated pathname '':'' -> '1071_20100714185800.mpg'
2010-07-14 23:14:38.877 MainServer::ANN Monitor
2010-07-14 23:14:38.878 adding: server as a client (events: 2)
2010-07-14 23:14:38.892 MainServer::ANN Monitor
2010-07-14 23:14:38.892 adding: server as a client (events: 2)
2010-07-14 23:14:38.903 MainServer::ANN Monitor
2010-07-14 23:14:38.939 adding: server as a client (events: 2)
2010-07-14 23:14:57.489 AudioOutput Error: Invalid channel count 6
2010-07-14 23:18:30.679 AutoExpire: CalcParams(): Max required Free Space: 10.0 GB w/freq: 15 min
2010-07-14 23:19:40.134 [ac3 @ 0xb65ca960]frame CRC mismatch
2010-07-14 23:19:40.163 [ac3 @ 0xb65ca960]frame sync error
2010-07-14 23:19:40.164 AFD Error: Unknown audio decoding error
2010-07-14 23:19:40.629 [mpeg2video @ 0xb65ca960]slice mismatch
2010-07-14 23:19:40.631 [mpeg2video @ 0xb65ca960]Warning MVs not available
2010-07-14 23:23:09.281 [mpeg2video @ 0xb65ca960]invalid mb type in B Frame at 14 17
2010-07-14 23:23:09.281 [mpeg2video @ 0xb65ca960]invalid mb type in B Frame at 56 18
2010-07-14 23:23:09.283 [mpeg2video @ 0xb65ca960]Warning MVs not available
2010-07-14 23:28:56.940 [mpeg2video @ 0xb65ca960]ac-tex damaged at 26 38
2010-07-14 23:28:56.941 [mpeg2video @ 0xb65ca960]ac-tex damaged at 8 27
2010-07-14 23:28:56.941 [mpeg2video @ 0xb65ca960]ac-tex damaged at 60 28
2010-07-14 23:28:56.942 [mpeg2video @ 0xb65ca960]ac-tex damaged at 7 30
2010-07-14 23:28:56.942 [mpeg2video @ 0xb65ca960]invalid cbp at 27 30
2010-07-14 23:28:56.942 [mpeg2video @ 0xb65ca960]invalid cbp at 75 31
2010-07-14 23:28:56.943 [mpeg2video @ 0xb65ca960]ac-tex damaged at 9 32
2010-07-14 23:28:56.943 [mpeg2video @ 0xb65ca960]ac-tex damaged at 24 35
2010-07-14 23:28:56.944 [mpeg2video @ 0xb65ca960]ac-tex damaged at 15 34
2010-07-14 23:28:56.944 [mpeg2video @ 0xb65ca960]ac-tex damaged at 0 36
2010-07-14 23:28:56.945 [mpeg2video @ 0xb65ca960]ac-tex damaged at 24 37
2010-07-14 23:28:56.945 [mpeg2video @ 0xb65ca960]ac-tex damaged at 12 39
2010-07-14 23:28:56.945 [mpeg2video @ 0xb65ca960]ac-tex damaged at 4 41
2010-07-14 23:28:56.946 [mpeg2video @ 0xb65ca960]ac-tex damaged at 7 42
2010-07-14 23:28:56.946 [mpeg2video @ 0xb65ca960]ac-tex damaged at 1 43
2010-07-14 23:28:56.946 [mpeg2video @ 0xb65ca960]ac-tex damaged at 0 44
2010-07-14 23:32:09.302 [ac3 @ 0xb65ca960]frame CRC mismatch
2010-07-14 23:32:09.333 [ac3 @ 0xb65ca960]frame sync error
2010-07-14 23:32:09.334 AFD Error: Unknown audio decoding error
2010-07-14 23:32:09.801 [mpeg2video @ 0xb65ca960]ac-tex damaged at 27 19
2010-07-14 23:33:22.208 UPnpMedia: BuildMediaMap VIDEO scan starting in :/var/lib/mythtv/videos:
2010-07-14 23:33:22.208 UPnpMedia: BuildMediaMap Done. Found 0 objects
2010-07-14 23:33:30.735 AutoExpire: CalcParams(): Max required Free Space: 10.0 GB w/freq: 15 min
2010-07-14 23:40:32.192 AudioOutput Error: Invalid channel count 6
2010-07-14 23:48:30.790 AutoExpire: CalcParams(): Max required Free Space: 10.0 GB w/freq: 15 min
2010-07-15 00:03:28.211 UPnpMedia: BuildMediaMap VIDEO scan starting in :/var/lib/mythtv/videos:
2010-07-15 00:03:28.211 UPnpMedia: BuildMediaMap Done. Found 0 objects
2010-07-15 00:03:30.845 AutoExpire: CalcParams(): Max required Free Space: 10.0 GB w/freq: 15 min
2010-07-15 00:17:23.264 [mpeg2video @ 0xb65ca960]ac-tex damaged at 63 22
2010-07-15 00:17:23.264 [mpeg2video @ 0xb65ca960]invalid cbp at 42 23
2010-07-15 00:17:23.264 [mpeg2video @ 0xb65ca960]ac-tex damaged at 33 26
2010-07-15 00:17:53.807 AudioOutput Error: Invalid channel count 6
2010-07-15 00:18:05.215 [ac3 @ 0xb65ca960]frame CRC mismatch
2010-07-15 00:18:05.242 [ac3 @ 0xb65ca960]frame sync error
2010-07-15 00:18:05.243 AFD Error: Unknown audio decoding error
2010-07-15 00:18:05.643 [mpeg2video @ 0xb65ca960]invalid cbp at 71 23
2010-07-15 00:18:05.644 [mpeg2video @ 0xb65ca960]invalid mb type in B Frame at 35 28
<snip: more of the same>
2010-07-15 00:36:51.199 [mpeg2video @ 0xb65ca960]mb incr damaged
2010-07-15 00:36:51.200 [mpeg2video @ 0xb65ca960]invalid cbp at 7 33
2010-07-15 00:36:51.200 [mpeg2video @ 0xb65ca960]ac-tex damaged at 43 34
2010-07-15 00:36:51.201 [mpeg2video @ 0xb65ca960]ac-tex damaged at 27 35
2010-07-15 00:36:51.201 [mpeg2video @ 0xb65ca960]slice mismatch
2010-07-15 00:36:51.209 [mpeg2video @ 0xb65ca960]ac-tex damaged at 0 37
2010-07-15 00:36:51.209 [mpeg2video @ 0xb65ca960]ac-tex damaged at 36 38
2010-07-15 00:36:51.210 [mpeg2video @ 0xb65ca960]mb incr damaged
2010-07-15 00:36:51.210 [mpeg2video @ 0xb65ca960]ac-tex damaged at 1 40
2010-07-15 00:36:51.211 [mpeg2video @ 0xb65ca960]slice mismatch
2010-07-15 00:36:51.211 [mpeg2video @ 0xb65ca960]slice mismatch
2010-07-15 00:36:51.212 [mpeg2video @ 0xb65ca960]invalid mb type in B Frame at 42 43
2010-07-15 00:36:51.212 [mpeg2video @ 0xb65ca960]ac-tex damaged at 0 44
2010-07-15 00:38:33.934 AudioOutput Error: Invalid channel count 6
2010-07-15 00:48:31.045 AutoExpire: CalcParams(): Max required Free Space: 10.0 GB w/freq: 15 min
2010-07-15 00:48:59.777 AudioOutput Error: Invalid channel count 6
2010-07-15 00:59:35.044 [ac3 @ 0xb65ca960]incomplete frame
2010-07-15 00:59:36.211 Transcoding /var/lib/mythtv/recordings/1071_20100714185800.mpg done
2010-07-15 00:59:36.236 Requesting delete for file 'myth://Default@192.168.0.1:6543/1071_20100714185800.mpg.old'.
2010-07-15 00:59:36.238 ProgramInfo(): Updated pathname '':'' -> '1071_20100714185800.nuv'
2010-07-15 00:59:36.277 MainServer::ANN Playback
2010-07-15 00:59:36.298 adding: server as a client (events: 0)
Error in my_thread_global_end(): 1 threads didn't exit
2010-07-15 00:59:41.485 transcode: Transcode Finished: So You Think You Can Dance: Autodetect (6.1 GB)
2010-07-15 00:59:41.485 JobQueue: Transcode Finished: So You Think You Can Dance: Autodetect (6.1 GB)
2010-07-15 00:59:41.533 ProgramInfo(): Updated pathname '':'' -> '1071_20100714185800.nuv'

I've definitely been seeing the same slowdown, but I'll run some tests to confirm it's the same issue. The odd thing is that this isn't impacting any of my SD recordings and I could have sworn it was channel specific. I suspect this probably started when I upgraded to a a 0.23 RPM.

Finally I see someone else with the same issues I've had! I've posted a number of times on various forums about this and never had a solution. The best I could find was some sort of bug in the ffmpeg code for mythtv.

For me the SD was fine but anything HD (720p, 1080i) would fail in this way.

Originally Posted by Lost Dog

Finally I see someone else with the same issues I've had! I've posted a number of times on various forums about this and never had a solution. The best I could find was some sort of bug in the ffmpeg code for mythtv.

For me the SD was fine but anything HD (720p, 1080i) would fail in this way.

Did anybody get a definate resolution on this one? I have the following to add:

It appears to be related to streams broadcast in 5.1 audio. When I transcode I get the following error: "AudioOutput Error: Invalid channel count 6".

For a while, I was running a mythtranscode from the SVN repository and that worked fine. What I had found was that the atrpms RPMs worked fine transcoding on my laptop (Core 2 Duo), but not on my backend box (AMD Phenom). I compiled from SVN and things were great.

Now the issue is back again with the latest update (to the new git repo). It's not the CPU this time, so I'm back at square one. I believe someone said it may be related to an upstream ffmpeg issue, but I can't find info on that from uncle google.

Thoughts?

--bryan

Mythtranscode is really very limited. If actually re-encoding, it is only capable of MPEG4 (ASP) and RTJPEG. MPEG4 is not a substantial improvement over MPEG2, and was really never designed for high quality, high bitrate content. RTJPEG on the other hand is vastly inferior to either, and its only purpose is to provide something that underpowered systems can compress framegrabbers to, when they are too slow to manage MPEG4 in real time.

Either stick to lossless commercial clipping, or use some tool other tham mythtranscode.

Originally Posted by wagnerrp

Mythtranscode is really very limited. If actually re-encoding, it is only capable of MPEG4 (ASP) and RTJPEG. MPEG4 is not a substantial improvement over MPEG2, and was really never designed for high quality, high bitrate content. RTJPEG on the other hand is vastly inferior to either, and its only purpose is to provide something that underpowered systems can compress framegrabbers to, when they are too slow to manage MPEG4 in real time.

Either stick to lossless commercial clipping, or use some tool other tham mythtranscode.

But, mythtranscode should not destroy recordings.... In this case, the audio is at 1/3 speed so it's clearly a bug. It doesn't appear to happen to everyone, so my guess is it's something simple. Possibly related to a dependant library.

Perhaps, but in my opinion, its a bug that no one should be experiencing, as no one should be performing the steps necessary to exhibit that bug.

Originally Posted by wagnerrp

Perhaps, but in my opinion, its a bug that no one should be experiencing, as no one should be performing the steps necessary to exhibit that bug.

???? What steps? I simply installed mythtv from the atrpms repo. It worked for a while (pre 0.23) and I haven't been able to transcode reliably since.

The steps would be... using mythtranscode to do anything but a lossless commercial removal. Mythtranscode is at best outdated. There are better tools, better codecs, and better containers to use than it supports.