As we are being subjective, this thread gets long quick. I'm going to try and trim it keeping the interesting bits.
This go around is comparing a good (video/audio in sync) OTA NTSC file w/a OTA ATSC HDTV w/2.1 AC3 file that has been transcoded using Roger's script. The transcoded file appears to have sync problems everywhere except when using mythfontend (i.e. mplayer). Any help as to what we might do to tweak it is appreciated. Roger's script is located in the wiki: http://mvpmc.wikispaces.com/transcoding >> Roger Heflin wrote: >> >>> The script does attempt to determine the bitrate, and stream types >>> of the original file and only adjust as much as necessary, If the >>> bitrate is above 10 it cuts it down, if the resolution is above 640x480 >>> it cuts that down, and it adjusts the bitrate (up or down) based on >>> the resolution reduction/increate being done. >>> >>> The ones that I have transcoded appear to work correctly on the mvpmc, >>> on the things that are original SD mpeg/ac3 streams it coverts the AC3 >>> to mp3 and leaves the video as it was originally encoded, the resulting >>> mp3 audio appears to be in sync, at least so far I have not noticed >>> it being out of sync. >>> ... > Something I noted in the past. > > I did not always have audio sync issues, I started having the sync > issues when I changed the MythTV bitrate, before that > everything appeared to work correctly. After changing the bitrate the > audio tended to be out of sync some of the time even though testing > with mythfrontend and mplayer showed that the audio was perfectly > in sync. > > This has gotten alot better with the new mvpmc version, but it appears > to me that bitrate has some bearing on the audio being in sync or not. > > U would expect the ATSC OTA SD stuff to have a much higher bitrate then > most of your recordings. > > Roger I did some more testing using a SigmaDesign / SyabasLinux box. Started out with: ------------------------------------------------------ OTA ATSC HDTV w/2.1 AC3 audio. Ended up with: ------------------------------------------------------ Something I can play on MVPMC: ---------- ID_VIDEO_ID=0 ID_AUDIO_ID=0 MPEG-PS file format detected. VIDEO: MPEG2 640x480 (aspect 1) 29.970 fps 5924.0 kbps (740.5 kbyte/s) ID_FILENAME=2051_20071018193000.mpg ID_DEMUXER=mpegps ID_VIDEO_FORMAT=0x10000002 ID_VIDEO_BITRATE=5924000 ID_VIDEO_WIDTH=640 ID_VIDEO_HEIGHT=480 ID_VIDEO_FPS=29.970 ID_VIDEO_ASPECT=0.0000 ID_AUDIO_FORMAT=80 ID_AUDIO_BITRATE=0 ID_AUDIO_RATE=0 ID_AUDIO_NCH=0 ID_LENGTH=1792.79 ========================================================================== Opening video decoder: [mpegpes] MPEG 1/2 Video passthrough VDec: vo config request - 640 x 480 (preferred colorspace: Mpeg PES) Could not find matching colorspace - retrying with -vf scale... Opening video filter: [scale] VDecoder init failed :( Opening video decoder: [libmpeg2] MPEG 1/2 Video decoder libmpeg2-v0.4.0b Selected video codec: [mpeg12] vfm: libmpeg2 (MPEG-1 or 2 (libmpeg2)) ========================================================================== ID_VIDEO_CODEC=mpeg12 ========================================================================== Opening audio decoder: [mp3lib] MPEG layer-2, layer-3 AUDIO: 48000 Hz, 2 ch, s16le, 160.0 kbit/10.42% (ratio: 20000->192000) ID_AUDIO_BITRATE=160000 ID_AUDIO_RATE=48000 ID_AUDIO_NCH=2 Selected audio codec: [mp3] afm: mp3lib (mp3lib MPEG layer-2, layer-3) ========================================================================== AO: [alsa] 48000Hz 2ch s16le (2 bytes per sample) ID_AUDIO_CODEC=mp3 Starting playback... VDec: vo config request - 640 x 480 (preferred colorspace: Planar YV12) VDec: using Planar YV12 as output csp (no 0) Movie-Aspect is 1.33:1 - prescaling to correct movie aspect. ID_VIDEO_ASPECT=1.3333 VO: [xv] 640x480 => 640x480 Planar YV12 ---------- Mythfrontend: ------------------------------------------------------ Looks good, in sync. MVPMC: ------------------------------------------------------ Looks to be 1 to a faction of a second out of sync. It looks like the video is leading the audio most if not all the time. Skipping around sometimes helps. SigmaDesign/Syabas: ------------------------------------------------------ Looks to be a just a fraction of a second out of sync. The video is leading the audio. The problem appears to be consistent and the same even after skipping around. The digital output of the show on this box was AC3 2.1 audio. Now, after transcoding, it is 48KHz stereo. Then I tried an OTA NTSC recording: ---------- ID_VIDEO_ID=0 ID_AUDIO_ID=0 MPEG-PS file format detected. VIDEO: MPEG2 480x480 (aspect 2) 29.970 fps 6000.0 kbps (750.0 kbyte/s) ID_FILENAME=1007_20071011200000.mpg ID_DEMUXER=mpegps ID_VIDEO_FORMAT=0x10000002 ID_VIDEO_BITRATE=6000000 ID_VIDEO_WIDTH=480 ID_VIDEO_HEIGHT=480 ID_VIDEO_FPS=29.970 ID_VIDEO_ASPECT=0.0000 ID_AUDIO_FORMAT=80 ID_AUDIO_BITRATE=0 ID_AUDIO_RATE=0 ID_AUDIO_NCH=0 ID_LENGTH=3715.28 ========================================================================== Opening video decoder: [mpegpes] MPEG 1/2 Video passthrough VDec: vo config request - 480 x 480 (preferred colorspace: Mpeg PES) Could not find matching colorspace - retrying with -vf scale... Opening video filter: [scale] VDecoder init failed :( Opening video decoder: [libmpeg2] MPEG 1/2 Video decoder libmpeg2-v0.4.0b Selected video codec: [mpeg12] vfm: libmpeg2 (MPEG-1 or 2 (libmpeg2)) ========================================================================== ID_VIDEO_CODEC=mpeg12 ========================================================================== Opening audio decoder: [mp3lib] MPEG layer-2, layer-3 AUDIO: 48000 Hz, 2 ch, s16le, 384.0 kbit/25.00% (ratio: 48000->192000) ID_AUDIO_BITRATE=384000 ID_AUDIO_RATE=48000 ID_AUDIO_NCH=2 Selected audio codec: [mp3] afm: mp3lib (mp3lib MPEG layer-2, layer-3) ========================================================================== AO: [alsa] 48000Hz 2ch s16le (2 bytes per sample) ID_AUDIO_CODEC=mp3 Starting playback... VDec: vo config request - 480 x 480 (preferred colorspace: Planar YV12) VDec: using Planar YV12 as output csp (no 0) Movie-Aspect is 1.33:1 - prescaling to correct movie aspect. ID_VIDEO_ASPECT=1.3333 VO: [xv] 480x480 => 640x480 Planar YV12 Exiting... (Quit) ---------- Mythfrontend: ------------------------------------------------------ Looks good, in sync. MVPMC: ------------------------------------------------------ Looks good, in sync. SigmaDesign/Syabas: ------------------------------------------------------ Looks good, in sync. The differences in the files are: 1) Name 2) Video: problem recording (remember: OTA NTSC): VIDEO: MPEG2 640x480 (aspect 1) 29.970 fps 5924.0 kbps (740.5 kbyte/s) good recording (remember: OTA ATSC HDTV w/1.2 AC3 -> transcoded): VIDEO: MPEG2 480x480 (aspect 2) 29.970 fps 6000.0 kbps (750.0 kbyte/s) 3) Bitrate: problem recording: ID_VIDEO_BITRATE=5924000 good recording: ID_VIDEO_BITRATE=6000000 4) Width: problem recording: ID_VIDEO_WIDTH=640 good recording: ID_VIDEO_WIDTH=480 5) ID length: problem recording: ID_LENGTH=1792.79 good recording: ID_LENGTH=3715.28 6) And something about the audio bit rate I don't understand: problem recording: AUDIO: 48000 Hz, 2 ch, s16le, 160.0 kbit/10.42% (ratio: 20000->192000) ID_AUDIO_BITRATE=160000 good recording: AUDIO: 48000 Hz, 2 ch, s16le, 384.0 kbit/25.00% (ratio: 48000->192000) ID_AUDIO_BITRATE=384000 ...thoughts? ------------------------------------------------------------------------- This SF.net email is sponsored by: Splunk Inc. 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