In the discussion of having a freedom-friendly camcorder or other video device, we discussed the idea of using intra-only Theora video to make post-recording editing a much easier process, allowing things like frame-by-frame editing without the need to decode and reencode the video again, thus incurring loss. I was quite skeptical of the efficiency of intra-only Theora, and I had speculated that the quality difference between intra-only Theora video (using the latest ptalarbvorm code) and, say, MJPEG video, wouldn't be much. I decided to test this theory, and so I pulled down some real HD 1080p videos from the Xiph media site (http://media.xiph.org) and decided to test intra-only Theora and MJPEG at 25Mbps with the test clips. I used the encoder_example that's packaged with libtheora to create the Ogg Theora files, while I used ffmpeg from SVN (could be a few months old) to create the MJPEG AVI video files. The test files & results can be found here: http://media.basilgohar.com/intra-comparison/ I have also setup an rsync module for the intra comparison, so you can pull down everything (or take your pick of what to pull down) via anonymous rsync, as well: rsync://media.basilgohar.com/intra-comparison/ You are welcome to see the results for yourself, but in short, in all case, Theora Intra (TheoraPro?) far outclassed MJPEG in terms of quality, which pleasantly surprised me. It is for this reason I have gone to these lengths to make this comparison widely available. In some cases, the rate control for the MJPEG went haywire, so you'll find that some of the MJPEG clips are much larger than the Ogg Theora clips. This is a testament to ptalarbvorm's rate control - it did not veer much at all from the target rate even when faced with some difficult-to-encode frames. I think this test is a useful one in demonstrating Theora's feasibility as a high-quality, intra-only codec. Furthermore, it also shows that even in such a simple case as an intra frame (a.k.a., keyframe), gains can be had, as gmaxwell observed that some optimizations could made to improve quality even further. So, it is my hope that this test will spur further interest in Theora as a consumer video device codec, and in particular, an intra-only subset of the libtheora codec. I am looking forward to further improvements in this area, and I hope to be able to bring reports of improvements as libtheora development progresses. P.S. I have been encouraged to make a blog post about this, and if I find the time to do so, I will, and I will share a link to it (with possible screenshots and further analysis). -- *Basil Mohamed Gohar* abu_hurayrah at hidayahonline.org http://www.basilgohar.com/blog/ IslamicHomeschool.com - Islamic Education for the Home <http://www.islamichomeschool.com/>
Basil, Let me (as a camera designer/maker) remind you what I wrote earlier - for the video recording standard MJPEG and intra-only Theora are sub-optimal. It seems to be more practical to record compressed Bayer data from the sensor so the recorded data preserves virtually the same information as real "raw", just using less bandwidth/data storage - compression is based not just on the human perception (as in most image/video compression formats) but on the noise model of the sensor (eliminating "garbage" data from the sensor output) . Theora is great for distributing video, but (as is) it is not optimal for the video recording purposes. Maybe it is possible to make a "flavor" of it suitable for compressing raw Bayer pixels similarly to what we were doing with JP4 as a modification of the standard JPEG. Andrey -------------- next part -------------- An HTML attachment was scrubbed... URL: http://lists.xiph.org/pipermail/theora/attachments/20100512/e6adefe9/attachment.htm
Basil... I am excited at the discussion thus far. We really need a camcorder for the masses that is truly free. In free I mean free to use for professional and personal use. I aspire to become a videographer in the near future and I can say that I was taken aback when I learned of MPEG-LA and the royalties. I am looking forward to seeing http://www.librevideo.org On May 12, 2010, at 10:56 AM, Basil Mohamed Gohar wrote:> In the discussion of having a freedom-friendly camcorder or other video > device, we discussed the idea of using intra-only Theora video to make > post-recording editing a much easier process, allowing things like > frame-by-frame editing without the need to decode and reencode the video > again, thus incurring loss. > > I was quite skeptical of the efficiency of intra-only Theora, and I had > speculated that the quality difference between intra-only Theora video > (using the latest ptalarbvorm code) and, say, MJPEG video, wouldn't be > much. I decided to test this theory, and so I pulled down some real HD > 1080p videos from the Xiph media site (http://media.xiph.org) and > decided to test intra-only Theora and MJPEG at 25Mbps with the test > clips. I used the encoder_example that's packaged with libtheora to > create the Ogg Theora files, while I used ffmpeg from SVN (could be a > few months old) to create the MJPEG AVI video files. > > The test files & results can be found here: > > http://media.basilgohar.com/intra-comparison/ > > I have also setup an rsync module for the intra comparison, so you can > pull down everything (or take your pick of what to pull down) via > anonymous rsync, as well: > > rsync://media.basilgohar.com/intra-comparison/ > > You are welcome to see the results for yourself, but in short, in all > case, Theora Intra (TheoraPro?) far outclassed MJPEG in terms of > quality, which pleasantly surprised me. It is for this reason I have > gone to these lengths to make this comparison widely available. > > In some cases, the rate control for the MJPEG went haywire, so you'll > find that some of the MJPEG clips are much larger than the Ogg Theora > clips. This is a testament to ptalarbvorm's rate control - it did not > veer much at all from the target rate even when faced with some > difficult-to-encode frames. > > I think this test is a useful one in demonstrating Theora's feasibility > as a high-quality, intra-only codec. Furthermore, it also shows that > even in such a simple case as an intra frame (a.k.a., keyframe), gains > can be had, as gmaxwell observed that some optimizations could made to > improve quality even further. So, it is my hope that this test will > spur further interest in Theora as a consumer video device codec, and in > particular, an intra-only subset of the libtheora codec. I am looking > forward to further improvements in this area, and I hope to be able to > bring reports of improvements as libtheora development progresses. > > P.S. I have been encouraged to make a blog post about this, and if I > find the time to do so, I will, and I will share a link to it (with > possible screenshots and further analysis). > -- > *Basil Mohamed Gohar* > abu_hurayrah at hidayahonline.org > http://www.basilgohar.com/blog/ > > IslamicHomeschool.com - Islamic Education for the Home > <http://www.islamichomeschool.com/> > _______________________________________________ > theora mailing list > theora at xiph.org > http://lists.xiph.org/mailman/listinfo/theora