Hi guys - I've some done work on ffmpeg's DV codec recently, on contract for some of my clients. Quality-wise, the video encoder should be competitive with popular commerical encoders. In some of my benchmarks it attains higher image quality than Apple's software encoder. Which is not to say it is 100% robust against all kinds of different input. It could certainly benefit from more exhaustive tuning.
Note: one small patch I submitted this February (SVN rev 5074) greatly improves encoded image quality by tweaking the DCT block class number assignment scheme. So you should definitely be testing with at least that version of ffmpeg. Off the top of my head, here are some of the remaining limitations: - ffmpeg does not do a particularly good job of resampling chroma channels between 4:2:2 and 4:2:0/4:1:1. (the recent libswscale patch may have fixed this, I'm not sure... before that, it was just using a box filter). - ffmpeg's DV encoder does not take any special care to do lossless re-encoding of macroblocks that have already been run through a DV codec. (although it will reproduce 8-bit Y'CbCr values accurately, so at least you don't have to worry about luma/chroma shifts). - it might be possible to improve perceived image quality by adaptively tuning the DC coefficient weighing matrix. Currently the ffmpeg encoder uses the matrix given in the SMPTE spec. It appears that Apple's encoder intentionally deviates from the spec (exaggerating higher frequencies) to improve perceived image quality. - it may be possible to tune the macroblock quantization selection algorithm, making it search for optimal QNOs more exhaustively. (trading off speed for better image quality). - it may be possible to improve the algorithm for choosing bewteen "field mode" and "progressive mode" DCTs. - ffmpeg's DV-in-MOV encoding is broken. It does not insert the DV audio and header data into the embedded DV stream, as required by Quicktime. Regards, Dan ------------------------------------------------------------------------- Take Surveys. Earn Cash. Influence the Future of IT Join SourceForge.net's Techsay panel and you'll get the chance to share your opinions on IT & business topics through brief surveys - and earn cash http://www.techsay.com/default.php?page=join.php&p=sourceforge&CID=DEVDEV _______________________________________________ Mjpeg-users mailing list Mjpeg-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/mjpeg-users
