[MPlayer-users] Are mencoder lossless codecs really lossless?

Carl Eugen Hoyos cehoyos at ag.or.at
Tue Jul 9 15:04:56 CEST 2013

James Board <jpboard2 <at> yahoo.com> writes:

> Okay, so then if I start with some specific color space, 
> compress with the lossless codecs, and then transcode back 
> to that same original colorspace (assuming everything else 
> is the same too: resolution, frame-rate, etc), then the 
> frames should be exactly the same as the original (except 
> for maybe small round-off errors, or artifacts of that 
> nature)?

When using a lossless codecs, no small round-off errors and 
no artefacts are possible (assuming a bug-free encoder, 
this is of course impossible, but recent tests with ffv1 
were successful.)

The only possibility is that the original colourspace 
is not supported by the encoder, but this is not the 
case here, all three encoders support yuv422.
(x264 also supports it.)

Since you mention "frame-rate" above:
I don't think the frame-rate has any relevance here, 
it is the applications responsibility to produce 
correct timestamps at encoding and decoding, this 
has nothing (or at least not much) to do with the 
encoder (and does not affect the losslessness of 
the codec).

Please do not top-post here, Carl Eugen

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