Re: [rtcweb] H261/MPEG-1 video quality (was: I'd love it if patents evaporated)

[Justin Uberti <[e-mail]>]

Thanks. Performance at 256 kbps is clearly unacceptable, 1933 kbps is
pretty decent. Would be great to see a 512 kbps and 1024 kbps version to
understand where things go from bad to good.


On Fri, Nov 15, 2013 at 3:42 PM, Hervé W. <[e-mail]> wrote:

>  <http://ge.tt/2bp1Zrz> <http://ge.tt/2bp1Zrz> <http://ge.tt/2bp1Zrz>
> http://ge.tt/2bp1Zrz
>
> options used:
> mencoder.exe -ovc lavc -lavcopts vcodec=h261:vbitrate=256 -o
> irene-256k.h261.avi sign_irene_cif.y4m
>
> mencoder.exe -ovc lavc -lavcopts
> vcodec=h261:vbitrate=256:last_pred=3:predia=2:dia=2:precmp=2:cmp=2:subcmp=2:preme=2:mbd=0
> -o irene-256k.h261.miscoptions.avi sign_irene_cif.y4m
>
> mencoder.exe -ovc lavc -lavcopts
> vcodec=h261:vbitrate=15999:last_pred=3:predia=2:dia=2:precmp=2:cmp=2:subcmp=2:preme=2:mbd=0
> -o irene-highbitrate.h261.avi sign_irene_cif.y4m
>
> You can probably derive ffmpeg/avconv options from those.
>
> Notes
>
>    - There's a ticket open about h261
>    <https://trac.ffmpeg.org/ticket/3143>
>    https://trac.ffmpeg.org/ticket/3143
>    - 15999 kbps was not the bitrate irene-highbitrate ended up using;
>    that was more like 1933 kbps
>    - My untrained eye did not see any difference between
>    irene-256k.h261.avi and irene-256k.h261.miscoptions.avi but maybe most of
>    those options are (rightly) ignored for h261.
>
>
> - Hervé
>
> ------------------------------
> From: [e-mail]
> Date: Fri, 15 Nov 2013 14:00:50 -0800
> To: [e-mail]
> CC: [e-mail]
> Subject: Re: [rtcweb] H261/MPEG-1 video quality (was: I'd love it if
> patents evaporated)
>
>
> From what I understand, the clip from this thread was encoded using
> MPEG-1, not H.261. Aside from
> http://www-mobile.ecs.soton.ac.uk/peter/h261/, I don't think we have seen
> any samples of actual H.261 output that give a good indication of its
> suitability.
>
>
> On Fri, Nov 15, 2013 at 5:52 AM, cowwoc <[e-mail]> wrote:
>
>
> Excellent work Adam. I can't speak for others, but at 254 kbps (corrected
> figure from your follow-up post) H.261 is definitely "good enough" and
> better than an audio-only connection.
>
> Gili
>
>
> On 14/11/2013 6:16 PM, Adam Roach wrote:
>
> I sent a reply to this earlier, but just now realized that it went only to
> Justin, not to the list.
>
>
>  On 11/14/13 13:59, Justin Uberti wrote:
>
> Thanks, this is interesting. Is the ffmpeg 261 encoder limited to
> CIF/QCIF, or can you specify arbitrary sizes?
>
>
> It looks like the ffmpeg mpeg-1 coder works for arbitrary sizes. I'm not
> sure what the difference between mpeg-1 and H.261 are, though, so we could
> be talking apples and oranges (or at least apples and pears) here. I'll
> note that mpeg-1 came out in 1991, which is a good 22 years in the past.
> I'm not drawing IPR conclusions for you, but invite you to ponder the
> implications yourself.
>
> Following Maik's lead with the mpeg-1 js decoder, I put this together:
>
> https://dl.dropboxusercontent.com/u/53717247/mpg/maven.html
>
> ...with this commandline:
>
>   ffmpeg -i maven.mp4 -f mpeg1video -flags qprd -mbd rd -cmp rd -subcmp rd
> -mbcmp rd -precmp rd -trellis 2 -g 100 -vb 256k maven.mpg
>
> I don't really understand most of those options (I just cribbed them from
> Maik's example) or whether any of them would introduce more latency than is
> reasonable for a real-time conversation, but I will observe:
>
>    1. The encoder claims that it was performing on the order of 90 - 100
>    fps on my (admittedly modern) system;
>     2. The resolution is 640x360 (somewhat larger than DCIF);
>    3. The video is not, to my eye, unusable (draw your own conclusions,
>    as it's clearly not as nice as modern codecs);
>     4. At 74 seconds and 4.7 MBytes (i.e., 37.6 Mbits), this encoding
>    works out to 508 kbits/second total.
>
>
>
> Source video here, and NASA is acknowledged as the source of the material
> contained therein: http://www.youtube.com/watch?v=ijAO0FFExx0
>
> /a
>
>
>
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