[FFmpeg-devel] [PATCH] ffmpeg.c: allow ffmpeg to output stats for each video stream

[Wang Cao]

Sorry I probably confused you a little bit. I was not suggesting removing
anything. I tried to convince you that
there is some issue with the bitrate calculation.

>From your original comments:

> This changes the printed values
> ./ffmpeg -i ~/videos/matrixbench_mpeg2.mpg -qscale 2  -vframes 3 -an
> test2.avi
> frame=    3 fps=0.0 q=2.0 Lsize=      51kB time=00:00:00.12
> bitrate=3495.7kbits/s speed=  12x
> video:51kB audio:0kB subtitle:0kB other streams:0kB global headers:0kB
> muxing overhead: 11.128063%
> vs.
> frame=    3 fps=0.0 q=2.0 Lsize=      57kB time=00:00:00.12
> bitrate=3884.7kbits/s speed=11.2x
> video:51kB audio:0kB subtitle:0kB other streams:0kB global headers:0kB
> muxing overhead: 11.128063%
> the file is the same


After my change:

> frame=    3 fps=0.0 q=2.0 Lsize=      51kB time=00:00:00.12
> bitrate=3495.7kbits/s speed=  12x

Before my change(master branch)

> frame=    3 fps=0.0 q=2.0 Lsize=      57kB time=00:00:00.12
> bitrate=3884.7kbits/s speed=11.2x

The size is different (51 vs 57) because I display the stream size instead
of the total file size. I think stream size
is more suitable in this context with "frame, fps, time".
For bitrate, I use the stream size to calculate it and I think it's more
accurate.


On Thu, Jul 12, 2018 at 5:01 AM Michael Niedermayer <michael at niedermayer.cc>
wrote:

> On Wed, Jul 11, 2018 at 03:47:45PM -0700, Wang Cao wrote:
> > >
> > > This changes the printed values
> > > ./ffmpeg -i ~/videos/matrixbench_mpeg2.mpg -qscale 2  -vframes 3 -an
> > > test2.avi
> > > frame=    3 fps=0.0 q=2.0 Lsize=      51kB time=00:00:00.12
> > > bitrate=3495.7kbits/s speed=  12x
> > > video:51kB audio:0kB subtitle:0kB other streams:0kB global headers:0kB
> > > muxing overhead: 11.128063%
> > > vs.
> > > frame=    3 fps=0.0 q=2.0 Lsize=      57kB time=00:00:00.12
> > > bitrate=3884.7kbits/s speed=11.2x
> > > video:51kB audio:0kB subtitle:0kB other streams:0kB global headers:0kB
> > > muxing overhead: 11.128063%
> > > the file is the same
> >
> >
> > Thanks for pointing this out! I have noticed the change in the stats but
> I
> > think the change is correct. Before my patch, the bitrate calculation is
> > based on total_size as in
> >
> > >     oc = output_files[0]->ctx;
> > >     total_size = avio_size(oc->pb);
> >
> > If I understand this correctly, the size of whole file will be used to
> > calculate the bitrate which considers probably header overhead.
> >
> > I changed it to
> >
> > > total_size = ost->data_size;
> >
> > Therefore only the size of the stream under consideration will be used
> for
> > calculation.
> >
> > Please correct me if my understanding is wrong. Thanks!
>
> Do i understand correctly that you suggest to remove the display of the
> filesize and file bitrate ?
> And in its place would be a display of a randomly picked stream bitrate ?
>
>
> [...]
> --
> Michael     GnuPG fingerprint: 9FF2128B147EF6730BADF133611EC787040B0FAB
>
> If you fake or manipulate statistics in a paper in physics you will never
> get a job again.
> If you fake or manipulate statistics in a paper in medicin you will get
> a job for life at the pharma industry.
> _______________________________________________
> ffmpeg-devel mailing list
> ffmpeg-devel at ffmpeg.org
> http://ffmpeg.org/mailman/listinfo/ffmpeg-devel
>


-- 
Wang Cao