[mythtv-users] Re: Nuvexport - VCD Audio and Video TOO Fast

Mike Smith easygreenus at yahoo.com
Wed Dec 10 00:38:29 EST 2003


Hi,

Made the changes suggested.  No change.  You must
have a different version of nuvexport.  I have
the nuvexport-latest from about a week ago.  
Your line numbers did not line up, but I figured
out where to make the changes.

Some more data:

1)RH9
2)mythtv 0.12
3) btaudio
4) sampling rate of 32,000 ( default )

I picked a scene change in the program and timed
how long it took to reach it.  Watching in mythtv,
it took 120 seconds.  Watching on the VCD, it took
90 seconds.  120/90 = 1.3333.  The ratio of
41,100/32,000 = 1.38, as someone pointed out.
The audio is a little out of sync with the lips, but
it stays with the scene.  Its not like the situation 
where the audio starts out a little out of sync and
gets minutes out of sync by the first commercial.

Here's another interesting observation.  If I use the
debug option and choose SVCD, it asks for the audio
bitrate.  It shows 224 as the default because I 
changed the default to 224 to get the -b 224 in the
toolame command.  The debug output does NOT show the
toolame command.  It shows:

mythtranscode command:

nice -n 19 mythtranscode -p autodetect -c 1048 -s
2003-08-11-19-30-00 -f fifodir.18073 --fifosync

toolame command:

nice -n 19 ffmpeg -f s16le -ar 32000 -ac 2 -i
fifodir.18073/audout -vn -f wav - | nice -n 19 mp2enc
-V -s -o 1048_20030811193000_20030811200000.mp2

mpeg2enc command:

nice -n 19 ffmpeg -f rawvideo -s 640x480 -r 29.97 -i
fifodir.18073/vidout -f yuv4mpegpipe - | nice -n 19
yuvdenoise -r 16 | nice -n 19 yuvscaler -v 0 -n n -M
BICUBIC -O SVCD | nice -n 19 mpeg2enc --format 5
--quantisation 5 --quantisation-reduction 2
--video-bitrate 02500 --aspect 2 --frame-rate 4
--interlace-mode 1 --motion-search-radius 24
--video-buffer 230 --nonvideo-bitrate 0224
--sequence-length 795 --reduction-4x4 1
--reduction-2x2 1 --keep-hf -o
1048_20030811193000_20030811200000.m2v

multiplex command:

nice -n 19 tcmplex -m s -i
1048_20030811193000_20030811200000.m2v -p
1048_20030811193000_20030811200000.mp2 -o "junk.mpg"


Also,  NOTE that when I use the --debug flag and
select VCD,  I do not get debug output.  It starts
right into the mythtranscode stop.

Thanks,

Mike

 Re: Nuvexport - VCD Audio and Video TOO Fast  [In
reply to]   	
From: Chris Petersen <lists at forevermore.net>
>>From: Someone else
>> The other option offered was to resample the audio.
>> nuvexport does not support this and, since the
audio
>> and video are in sync, I don't understand how this
>> would fix the problem.
>
>standalone players are VERY VERY picky about audio
>sample rates. SVCD
>*must* be 44.1kHz unless you move into xsvcd land.
>Not sure about VCD,
>but I'm pretty sure it'll be a similar case.

>From memory, VCD is also 44.1kHz but 224kbps. As I
recall, an earlier version of nuvexport had the
wrong VCD args to toolame and mp2enc. I sent a patch
but I guess it got lost in Chris' queue because it
seems the current version does not have the correct
args either. Also, mp2enc has options to resample but
toolame doesn't, so I don't know if toolame uses the
recorded sample rate or not. If toolame doesn't
resample, you might want to try mp2enc instead.

In any case, the wrong args made my DVD player
do exactly as you described. I'll be sending Chris
a patch shortly, but you can fix it up yourself
on line 114 by supplying toolame with -m j -b 224
instead of -m j -b 192 and on line 118 by
supplying mp2enc with -V -s -o <blah> instead
of -b -r <blah> -s -o <blah>.

-Dennis

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