Re: [rtcweb] H261/MPEG-1 video quality

As I've stated multiple times before in my own posts, "H.261" is a 
placeholder for "any codec for which IPR has expired".

Feel free to propose alternate codecs, and I believe this detail should 
be explicitly mentioned in the upcoming "vote". Meaning, the option that 
talks about H.261 being MTI should clarify we're talking about a 
placeholder.

Gili

On 14/11/2013 8:37 PM, Stephan Wenger wrote:
> Folks,
> Please don't consider H.261 and MPEG-1 part 2 as being in the same 
> league in terms of coding efficiency or network friendliness.  They 
> clearly are not.
> H.261 is what many call the first generation video coding standard. 
>  MPEG-1 (and MPEG-2) are second generation.
> MPEG-1 has half-pel motion compensation.  H.261 has not.
> MPEG-1 has B frames.  H.261 has not.
> MPEG-1 has (arbitrary sized) slices that can be used for MTU size 
> matching (although they are not commonly used for that purpose). 
>  H.261 has not.  Instead, H.261 has the Group Of Block picture 
> segmentation mechanism, that is clearly more optimized for parallel 
> processing than for MTU size matching.
> MPEG-1 allows for significantly larger motion vectors (necessitated by 
> B frames and the resulting longer prediction interval, but can be used 
> even in P frame only coding).
> MPEG-1 has arbitrary picture sizes.  H.261 allows QCIF, CIF, and 4CIF 
> (in "still image" mode, designed for low frame rate application; could 
> run at high frame rate though).
> H.261 was ratified (in its first version) in 1988, and in the for all 
> practical purposes final version in 1989.  Most people believe that 
> all related patents have expired.
> MPEG-1 was ratified in late 1992.  Its "bug fix" successor MPEG-2 
> (which adds interlace support) was ratified less than a year later. 
>  There are at least two major disputes going on today regarding 
> technology allegedly infringed by a compliant implementation of 
> MPEG-2.  Based on my technical understanding, one of these 
> technologies is not in any way related to interlaced.
> Draw your own conclusions.
> Regards,
> Stephan
>
>
>
>
> From: Adam Roach <adam@nostrum.com <mailto:adam@nostrum.com>>
> Date: Thursday, 14 November, 2013 at 15:22
> To: "rtcweb@ietf.org <mailto:rtcweb@ietf.org>" <rtcweb@ietf.org 
> <mailto:rtcweb@ietf.org>>
> Subject: Re: [rtcweb] H261/MPEG-1 video quality
>
> On 11/14/13 17:16, Adam Roach wrote:
>> # At 74 seconds and 4.7 MBytes (i.e., 37.6 Mbits), this encoding works 
>> out to 508 kbits/second total.
>
> Whoops, I messed up my math. It's 148 seconds long, not 74 (Quicktime 
> seems to divide it by two for some reason, although the javascript 
> decode does the right thing). This works out to 254 kbps.
>
> /a
>
>
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