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List:       olpc-devel
Subject:    codec optimization
From:       jochang () gmail ! com (Chih-Chung Chang)
Date:       2007-02-27 8:12:42
Message-ID: 5be3f210702270512m77211e3aqe76a15ace341843f () mail ! gmail ! com
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On 2/27/07, Albert Cahalan <acahalan@gmail.com> wrote:
> On 2/26/07, Chih-Chung Chang <jochang@gmail.com> wrote:
> > On 2/26/07, Albert Cahalan <acahalan@gmail.com> wrote:
> > >
> > > (BTW, I can imagine a fine low-CPU codec. You can use
> > > 100% P-frames w/o motion vectors if the decompressor
> > > is carefully specified regarding rounding. Start the stream
> > > with an implied solid-color frame, probably grey. Cuts and
> > > joins can be done anywhere at the cost of one or two
> > > recompressed frames.)
> >
> > I think this can be done by using the INTER_NOMV mode in Theora.
>
> That sounds like I-frames, not P-frames. P-frames depend on
> preceding frames. Normally you can't keep going with them
> forever because round-off errors in the decoder will accumulate.
> If the decoder is more standardized though, the encoder could
> determine exactly what the decoder is using as a reference.

The coding mode for I-frames is INTRA. INTER_NOMV (and other modes)
are for P-frames. The IDCT in Theora is specified exactly.

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