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

[cowwoc <[e-mail]>]

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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