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 <cowwoc@bbs.darktech.org> 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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