---------- Forwarded message ----------
From: Muras <[email protected]>
Date: Wed, Jun 9, 2010 at 4:00 PM
Subject: [libav-user] How to solve this monotone timestamp issue for h.264?
To: [email protected], [email protected]
Dear Sir,
I am getting the below error message when i try to transcode
from any format to H.264 video and aac audio, I am new to ffmpeg, and am
missing something , here is that error message,
And the output is a loop of
error, non monotone timestamps 169 >= 169
error, non monotone timestamps 169 >= 169
error, non monotone timestamps 169 >= 169
error, non monotone timestamps 169 >= 169
Also i am getting some warning message stating tat
Non-strictly-monotonic PTS,
I saw somewher this warning can be eliminated if i set vfr as 0, can you
tell me how i can set this parameter in codeccontext structure, (not through
command line , i need to do in source)
Can you please help me out on this sir, i am strugling with this issue more
than 2 weeks.
thanks
Muras K
On Tue, Jun 8, 2010 at 1:37 PM, Tomas Härdin <[email protected]>wrote:
> On Mon, 2010-06-07 at 19:55 -0400, [email protected] wrote:
> > I am working on integrating a new video encoder. One issue I am having
> > is determining the frame rate of the input video stream. The is
> > available in the AVFormatContext but not in the AVCodecContext. The
> > AVCodecContext does contain a time_base value but this does not seem to
> > translate properly into a frame rate in all cases. There are some
> > video streams where the time_base is 50 / 2997 which would come to
> > 59.94 fps. However, the AVFormatContext indicates the frame rate is
> > 29.92 fps. I believe the actual frame rate is more likely the 29.92
> > value, however, this is not available at the libavcodec scope. Is
> > there any undocumented process for determining the actual frame rate at
> > the libavcodec scope?? I also tried using the pts value in the AVFrame
> > structure from the decoded frame. This turned out not to be provided
> > by the decoder and is always 0.
> >
> > One example . . .
> > <<
> > Duration: 00:02:42.36, start: 0.000000, bitrate: 820 kb/s
> > Stream #0.0: Video: h264, yuv420p, 640x352 [PAR 1:1 DAR 20:11], 820
> > kb/s, 58.82 fps, 29.92 tbr, 1k tbn, 59.94 tbc
> > Stream #0.1: Audio: aac, 22050 Hz, stereo, s16
> > Output #0, flv, to '':
> > Stream #0.0: Video: libx264, yuv420p, 640x352, q=2-31, 650 kb/s,
> > 58.82 fps, 29.92 tbr, 1k tbn, 59.94 tbc
> > Stream #0.1: Audio: aac, 22050 Hz, stereo, s16
> > >>
> >
> > Here's a an even worse case . . .
> >
> > <<
> > Duration: 00:04:45.05, start: 0.000000, bitrate: 195 kb/s
> > Stream #0.0, 21, 1/1000: Video: h264, yuv420p, 320x214 [PAR 1:1 DAR
> > 160:107], 1/2000, 195 kb/s, 29.92 tbr, 1k tbn, 2k tbc
> > Stream #0.1, 15, 1/1000: Audio: aac, 22050 Hz, stereo, s16
> > Output #0, flv, to '':
> > Stream #0.0, 0, 1/1000: Video: libx264, yuv420p, 320x214, 1/2000,
> > q=2-31, 650 kb/s, 29.92 tbr, 1k tbn, 2k tbc
> > Stream #0.1, 0, 1/90000: Audio: aac, 22050 Hz, stereo, s16
> > >>
> >
>
> FLV has variable frame rate - the timestamps are always specified with a
> 1 kHz time base. It's fairly common for the "average" frame rate to
> vary. I've seen YouTube FLVs start at 3 fps, but switch to ~29.97 fps a
> few seconds later. In other words, in general lavf can't figure out the
> exact frame rate. Also, if I remember correctly the codec's time base is
> the field rate, which might in fact be useful (divide by 2 if
> interlaced).
>
> Your best bet would be to preserve the time stamps and convert them to
> the muxer's time base when written (av_rescale_q() between the
> AVFormatContext::time_base:es). If you want constant frame rate output
> you'll have to drop and/or duplicate frames to reach the desired rate.
> If you're outputing to flv again then you don't need to worry too much
> since the output is VFR too. You will need to give the encoder a frame
> rate guess for it to perform proper rate control though.
>
> I hope this helps a bit at least.
>
> /Tomas
>
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>
>
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