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List:       mjpeg-users
Subject:    Re: [Mjpeg-users] DV analyzer tool / optimizing video rendering?
From:       Dan Maas <dmaas () maasdigital ! com>
Date:       2006-11-29 17:07:54
Message-ID: 20061129170754.GA9184 () maasdigital ! com
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>   That's what I thought. So basically, if I understand you correctly
> the only application of such a lossless re-encoding would be to
> do a sort of "injection" of additional video material into an existing
> DV frame.

That's for sub-frame re-encoding. Yes, I'm not sure how much of a
benefit it would have, due to macroblocks in each video segment being
scattered all over the frame.

The original poster was complaining about image quality getting worse
after several re-compressions. This is a valid point to consider,
since not all editing systems and workflows are good at preserving
already-compressed frames. It is also a common benchmark that people
use to compare codecs. (although personally I have no motivation to
work on this, since I don't use DV as a master format anymore).

>   I've fixed that. Everything that doesn't require a knowledge of 
> frame counting or audio is now being inserted by a codec, not by
> a muxer. The only pieces left are those having to do with audio.
> Or may be you're saying that even this is not good enough for your
> application ?

Good, I wasn't aware of that change. The DV stream does need to have
embedded audio though. Otherwise there will be no audio when it is
played out to a FireWire device. When Quicktime applications play to
FireWire, they don't insert the audio based on the MOV audio track,
they just play the raw DV stream. (it's confusing because desktop
software like Quicktime Player DOES play the MOV audio track, ignoring
the embedded audio. But if you try to record the file to DV tape, it
only transmits the embedded DV stream).

Regards,
Dan

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