[mythtv-users] nuvexport created xvid files play fine on PC but have stutter and audio delay on TV

devsk funtoos at yahoo.com
Sat Jan 6 23:57:00 UTC 2007


answering my own question. I found that ffmpeg creates a more compliant avi compared to transcode, and fixed all my problems with sync and fast forward. I recently did a comparison of ffmpeg and transcode from nuvexport with the same settings. I found ffmpeg to be a winner in all aspects: quality, speed, compatibility and size closer to the specified bitrate. I have uploaded two frame grabs for comparison purposes

http://home.comcast.net/~funtoos/transcode.png
http://home.comcast.net/~funtoos/ffmpeg.png

transcode is a little more smoothed out: note the sharpness in curtain and sunlight falling on the door thru the curtain in ffmpeg on the left side of the grab, whereas they are so fuzzy in transcode. The avg. rate was 1471 for transcode and 1508 for ffmpeg, for a specified rate of 1500. mencoder went crazy with bitrates (used 2800 for a specified rate or 1500), so was ruled out.

-devsk
PS: first impression of ffmpeg being bad quality compared to transcode was a mistake based on lower bitrate (960) for ffmpeg, which was done earlier than transcode.

----- Original Message ----
From: devsk <funtoos at yahoo.com>
To: mythtv-users at mythtv.org
Sent: Wednesday, January 3, 2007 12:41:06 PM
Subject: [mythtv-users] nuvexport created xvid files play fine on PC but have stutter and audio delay on TV

Using a WinTV PVR USB2 I kept the original mpeg2 recordings and didn't transcode after recording. After that I did nuvexport-xvid --transcode on four of these, using cutlist, 2 pass VBR encoding at 1500kbps sized at 640x480. I then wrote these to a DVD-RW and played them on my standalone which plays previously encoded xvid files fine. The output was jerky and audio lost sync with video after a while.

Chosing de-interlace didn't make any difference to "jerkiness". ffmpeg created files had no such "jerkiness" and had RIFF header with ~30fps while transcode created RIFF header with 29.97fps which matches with the source fps of 29.97 as shown by mplayer. ffmpeg quality was pretty bad compared to transcode at the same bitrate and same encoder (xvid). None of the files allow fast forward faster than 2x. Audio
 sync delay and "jerkiness" are more pronounced if I fast forward. It doesn't happen with my older xvid files which I created using mencoder (I think), maybe a year ago.

In nutshell, I am confused as to what is causing the audio delays and jerkiness on TV. Could it be the standalone player? I am using Samsung  V5650 combo player. But I wonder why are the problems not present with older AVI files if its the player?

Any insights into the issues will be highly appreciated.

-devsk



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