onlydarksets

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Archive for the ‘ffmpeg’ Category

Roll your own YouTube (mirror)

Posted by onlydarksets on January 29, 2009

A while back I found a good post (via FlashInsider) that detailed how to create a video sharing site, but when I went to look at it recently, it was replaced by a placeholder page written in German.  Thanks to Google cache, here is a mirror of it, including comments.  I’m not planning on hosting a YouTube site, but the FLV/FlowPlayer stuff is interesting.

UPDATE: It’s back now, but I’m leaving this here anyway.

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Posted in ffmpeg | 6 Comments »

ffmpeg: “trell” errors

Posted by onlydarksets on September 24, 2008

I’ve found a few command lines to use ffmpeg to convert to iPod format, and they almost all use the “trell” flag.  I kept getting errors, and then I found that it is no longer a valid flag, so it needs to be removed from the command line.

And what is “trell”?  Not sure – something to do with quantization:

trell trellis quantization
this will find the optimal encoding for each 8×8 block
trellis quantization is quite simple a optimal quantization in the PSNR vs bitrate sense (assuming that there would be no rounding errors introduced by the IDCT, which is obviously not the case) it simply finds a block for the minimum of error + lambda*bits
lambda is a qp dependant constant
bits is the amount of bits needed to encode the block
error is simple the sum of squared errors of the quantization

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