If you’re in Dublin tomorrow (Saturday 28th March), and you’re interested in Open Source, feel free to come along to the OSSbarcamp at DIT Kevin St and enjoy some of the (completely free!) talks and demos. I’ll be presenting an introduction to the GStreamer multimedia framework in the afternoon.
Other talks I’ll be attending include my wife Jaime’s talk on using Git, Luis’ “Being Creative With Free Software”, and Stuart’s Advanced Javascript presentation.
I’d like to offer congratulations to all the Xiph folks, but especially Monty, Ralph and Tim on the theora-1.1alpha1 release from the Thusnelda encoder branch.
To try it out, I transcoded a short (1m40s) 720p trailer video from H.264+AAC to Theora+Vorbis, at libtheora quality setting of 32, using the 1.0 theora encoder, and again with 1.1. It’s not a very rigorous experiment, but enlightening nonetheless.
Both encoders produced output of comparable visual quality. With the 1.0 theora encoder the output file was 24383125 bytes. Of that, the video portion is about 1.835 Mbit/s. With libtheora 1.1alpha1, the same quality is reached with only 19088009 bytes (video at 1.416 Mbit/s)!
That’s a pretty easy 20-ish% compression improvement for no loss in quality. As an added bonus, the transcoding time dropped from 2m10s to 1m52s. That’s not quite real-time for this frame size in either case, but an impressive step closer.
There’s some degradation from the visual quality of the original file. That’s to be expected when taking a 5.61 Mbit/s video stream down to less than a third of the original size – even on the same codec.
For comparison, here’s a random frame from the output of each encoder, along with the same frame from the original file:
screenshot of the original H.264 framescreenshot from the theora-1.0 encodingscreenshot from the theora-1.1 encode
