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

Leon Geyser <lgeyser@gmail.com> Thu, 14 November 2013 19:35 UTC

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Date: Thu, 14 Nov 2013 21:35:32 +0200
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From: Leon Geyser <lgeyser@gmail.com>
To: "rtcweb@ietf.org" <rtcweb@ietf.org>
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Subject: Re: [rtcweb] H261/MPEG-1 video quality (was: I'd love it if patents evaporated)
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>>This includes a completely JavaScript-based MPEG-1 player for those that
don't happen to have a fitting decoder installed >>(also, yay, JavaScript
is fast enough now for simple video decoders!). I recreated the encoded
files to ensure there are no >>b-frames and documented the encoder settings
accordingly.
Thanks for sharing. Looks better than what I expected.

On 14 November 2013 21:12, Maik Merten <maikmerten@googlemail.com>; wrote:

> Hello again,
>
> to allow for having a quick look at some test sequences I put together a
> very very sloppy overview page at
>
> https://dl.dropboxusercontent.com/u/14053306/mpeg1/index.html
>
>
> This includes a completely JavaScript-based MPEG-1 player for those that
> don't happen to have a fitting decoder installed (also, yay, JavaScript is
> fast enough now for simple video decoders!). I recreated the encoded files
> to ensure there are no b-frames and documented the encoder settings
> accordingly.
>
> Best regards,
>
> Maik
>
>
> Am 14.11.2013 11:52, schrieb Maik Merten:
>
>  Hello all,
>>
>> in http://www.ietf.org/mail-archive/web/rtcweb/current/msg09721.html a
>> sample of H.261 video was provided, connected to a (rhetorical?)
>> question if this provided quality would be acceptable for users. Clearly
>> that provided sample is of very low and unacceptable quality.
>>
>> Just for comparison, here are two CIF samples at roughly 256k created by
>> a somewhat modern encoder (ffmpeg with rate/distortion optimization):
>>
>>
>> https://dl.dropboxusercontent.com/u/14053306/mpeg1/irene-256k.mpg
>>
>> https://dl.dropboxusercontent.com/u/14053306/mpeg1/mad900-256k.mpg
>>
>>
>> (encoded as MPEG-1 video, as the "h261" encoder in ffmpeg crashes when
>> using rate/distortion optimization. I understand MPEG-1 if used without
>> b-frames is similar to H.261 in coding efficiency, but mostly adds more
>> flexibility regarding frame sizes.
>>
>> ffmpeg -i sign_irene_cif.y4m -vcodec mpeg1video -mbd rd -trellis 2 -cmp
>> 2 -subcmp 2 -g 100  -vb 256k irene-256k.mpg )
>>
>> Even without formal testing it is obvious that H.261 and/or MPEG-1 video
>> is clearly outperformed in terms of coding efficiency by H.264 and VP8.
>> However, personally, speaking as an end-user, I would very much prefer
>> this video quality over audio-only calls (in cases where transcoding is
>> not available), as the video produced still carries useful information.
>> Also H.261/MPEG-1 is blazingly fast, can be dealt with in software, and
>> is not exceedingly difficult to implement.
>>
>> Of course a MTI codec with higher coding performance is much preferable.
>> However, if no such high-performance codec with licensing terms that are
>> acceptable for all communities can be agreed on I think it may be wise
>> to seriously evaluate the option of implementing an outdated codec for
>> the sake of interoperability. In practice, most calls will negotiate to
>> H.264 and VP8 anyways, but sporadic negotiation failures that are
>> difficult to account for by the user are still to be expected if no MTI
>> codec is defined at all.
>>
>>
>>
>> Best regards,
>>
>> Maik
>>
>
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