Some MythTV recording transcodes do not keep audio sync
Posted: 10 Apr 2008 15:37
I have been transcoding MythTV recordings (from MPEG2 to h264) with the following command line:
Now, that might be a mess (I'm not exactly an expert), but it gets the job done, most of the time. The result plays back on a PS3 and an Xbox 360, which I'm happy with. What I'm not happy with is that sometimes the result has an audio offset that's consistent throughout the recording. If I look at the original (MPEG2) with Media Info, it shows a "Video0 delay" in milliseconds, but if I look at the VLC output, there's nothing. I think I found an option in the help to do an offset (--audio-desync), but I can't really do batch scripting if I have to manually look up each and every audio offset myself.
This only seems to happen on certain recordings. Here's an example of before and after for a recording that *didn't* break:
Before:
After:
Can anyone help?
Code: Select all
c:\vlc\vlc -vvv --sout-transcode-deinterlace --sout-x264-level=41 %1 :sout=#transcode{vcodec=h264,vb=%2,scale=1,acodec=mp4a,ab=128,channels=2}:duplicate{dst=std{access=file,mux=mp4,dst="d:\mythtemp\temp.mp4"}} vlc:quitThis only seems to happen on certain recordings. Here's an example of before and after for a recording that *didn't* break:
Before:
Code: Select all
General #0
Complete name : \\192.168.42.102\myth\pretty\Mister Rogers' Neighborhood - 2008-02-27, 11-30 AM.mpg
Format : MPEG-2 Program
Format/Family : MPEG-2
File size : 1012 MiB
PlayTime : 28mn 31s
Bit rate : 4958 Kbps
Video #0
PlayTime : 28mn 31s
Bit rate : 4230 Kbps
Audio #0
Codec : MPEG-1 Audio layer 2
PlayTime : 28mn 31s
Bit rate mode : CBR
Bit rate : 384 Kbps
Channel(s) : 2 channels
Sampling rate : 48 KHz
Resolution : 16 bits
Video0 delay : 23ms
Writing library : Xing (new)Code: Select all
General #0
Complete name : D:\Archives\TV\Mister Rogers' Neighborhood - 2008-02-27, 11-30 AM.mp4
Format : MPEG-4
Format/Info : ISO 14496-1 Base Media
Format/Family : MPEG-4
File size : 232 MiB
PlayTime : 28mn 31s
Bit rate : 1137 Kbps
StreamSize : 1.72 MiB
Encoded date : UTC 2008-04-09 10:15:38
Tagged date : UTC 2008-04-09 10:15:38
SpecialPlaybackRequirements : QuickTime 6.0 or greater
©enc : vlc 0.8.6c stream output
Video #0
Codec : AVC
Codec/Family : AVC
Codec/Info : MPEG-4 AVC
Codec profile : Main@L4.1
Codec settings, CABAC : Yes
PlayTime : 28mn 31s
Bit rate : 1001 Kbps
Width : 720 pixels
Height : 480 pixels
Display Aspect ratio : 4/3
Frame rate : 29.970 fps
Minimum frame rate : 29.441 fps
Maximum frame rate : 30.333 fps
Standard : NTSC
Chroma : 4:2:0
Interlacement : Progressive
Bits/(Pixel*Frame) : 0.097
StreamSize : 204 MiB
Encoded date : UTC 2008-04-09 10:15:40
Tagged date : UTC 2008-04-09 10:15:40
Audio #0
Codec : AAC LC
Codec/Family : AAC
Codec/Info : AAC Low Complexity
PlayTime : 28mn 31s
Bit rate mode : VBR
Bit rate : 127 Kbps
Channel(s) : 2 channels
Channel positions : L R
Sampling rate : 48 KHz
Resolution : 16 bits
StreamSize : 26.0 MiB
Encoded date : UTC 2008-04-09 10:15:38
Tagged date : UTC 2008-04-09 10:15:38Can anyone help?