I have recently started to transfer some TV recordings onto DVD:s, using Fredrik Hubinette's mkdvd script. With high bitrates (~ 5.5Mbit/s) the quality was quite good, but when I tried a lower bitrate (~3.5 Mbit/s), I ended up with some horrible pulsating DCT blocks in otherwise quiet (almost still) backgrounds. These are very apparent both on my standalone DVD player (Philips HDR1000) and with mplayer (1.0pre3-3.3.3.) mkdvd is a wrapper script, tying together a number of tools in a pipeline, but the artifacts I got seemed to be introduced by mpeg2enc (v1.6.2, from the Debian mjpegtools package.)
From my experience with MPEG2 and DVB, I knew that 3.5 Mbit/s did not normally result in such horrible artifacts, so I started to search for explanations or workarounds on the Web. I found some helpful hints on this list, in a recent thread with the title "1.6.1.93: Bad quality." Decreasing the quality setting from the best one (-q 1) to a worse one (-q 4) produced a dramatic improvement in quality for me. However, there was not a linear improvement between these values, as "-q 3" rather seemed to cause the worst result. (Using "-R 2" to introduce B frames also helped a bit, but I think that worked more to cover up the symptoms of the real bug.)
This workaround works well enough for me, but in case someone is interested in tracking down the real problem, I thought I'd post some details to the list. I have put together a web page (http://westman.yi.org/ex1.html) containing input and output files from these scenarios (only a few seconds in length) along with the command line parameters used and some diagnostic output from mpeg2enc. There is also a screenshot zoomed in on an instance of the problem (from the "-q 1" run.)
--
Rickard Westman "Beware of the panacea peddlers: Just
<[EMAIL PROTECTED]> because you wind up naked doesn't
make you an emperor."
- Michael A Padlipsky------------------------------------------------------- This SF.Net email is sponsored by: IBM Linux Tutorials Free Linux tutorial presented by Daniel Robbins, President and CEO of GenToo technologies. Learn everything from fundamentals to system administration.http://ads.osdn.com/?ad_id=1470&alloc_id=3638&op=click _______________________________________________ Mjpeg-users mailing list [EMAIL PROTECTED] https://lists.sourceforge.net/lists/listinfo/mjpeg-users
