23 Mar 2003 raph   » (Master)

Other blog: Indymedia, news.google.com, Balochistan post, Reaching out

Home media

One of the big, huge potential killer apps for free software is to run home media centers, such as the ones that VIA is pushing with their C3 chip. With good support for non-DRM audio and video, and good p2p networking (such as BitTorrent), such a system could be overwhelmingly better than the crippled alternatives put out by mainstream corporations.

To this end, OpenShiiva looks particularly interesting. I haven't tried it yet, but it looks like it's addressing both quality and UI. The free MPEG2 tools I've played with so far have serious deficiencies in both departments.

One specific problem is that no free MPEG2 encoder I've seen can handle video sequences with mixed 29.997 fps and 24 fps 3:2 pulldown. The MPEG2 spec allows such mixing freely, through the "repeat first field" flag, which is independently settable for each frame. If it toggles on:off:on:off, it's 3:2 pulldown. If it's always off, it's 29.997 fps. Many DVD's mix the two, for example splicing a video-source animated logo on the front of a 24 fps movie.

Part of the problem is that yuv4mpeg format (used as the input to mpeg2enc) loses the RFF flag information. Thus, as you dig into the source code to tools such as transcode and mencoder, you tend to see a lot of crude hacks to work around the problem.

I've hacked up my local version of mpeg2enc to preserve the RFF flags from the source stream, with good results, but unfortunately the patches aren't general enough for production use; among other things, mplex'ing the resulting stream can result in underruns depending on the exact frame rate.

I have some notes on the pulldown issue that I'm planning on publishing as a Web page. Are there any MPEG2 encoder hackers who care?

Being nice

Zaitcev: passions are running high, on all sides. I ask you (and all Advogato posters) to be respectful of other people's opinions. There is no question that Bush is responsible for death and destruction on a large scale. Whether it's legal according to international law is one question. Whether it improves the situation for the Iraqi people is another (I honestly hope it does). Reasonable people can, and do, differ on these questions.

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