[theora] Theora Intra (ptalarbvorm) vs. MJPEG

Dave Johnson davefilms.us at gmail.com
Wed May 12 19:20:17 PDT 2010


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/>
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