Here's some quick data. For an approx 1 hour audio recording (of speech): Uncompressed:
WAV: 623M FLAC: 199M M4A: 120M (max quality setting in Audacity) MP2: 71M MP3: 57M FLAC did not show any compression gains using zip, MP3 compressed 3%, WAV compressed 33% to 419M (a lot worse than FLAC). So in our configuration I'd certainly be prepared to pay the extra size penalty (71M > 199M) to know that compression artefacts weren't negatively impacting speech recognition, for example. Is there a JIRA for this, or should I create one? Regards Stephen -- Stephen Marquard, Learning Technologies Co-ordinator Centre for Educational Technology, University of Cape Town http://www.cet.uct.ac.za Email / IM (Jabber/XMPP): [email protected] Phone: +27-21-650-5037 Cell: +27-83-500-5290 >>> Christopher Brooks <[email protected]> 4/14/2011 10:58 PM >>> Hi Stephen, I understand, I just think the bandwidth will be killer. But regardless, we did have arbitrary encoding profiles on the roadmap, though it is now delayed so I'm not sure when it will be coming (we will be reevluating). This would let you do aac, mp3, flac, etc.; whatever gstreamer can do (which is a fair bit) and perhaps more. Regards, Chris > AAC is also lossy though. The point of using a lossless compression H> in > the first (capture) phase is not to close-down or complicate > processing options that work best on uncompress formats. > > For example my simple tests on noise reduction with sox show that it > works very well on WAV audio, but is terrible on mp2 files. > > Similarly, speech recognition applications need 16 KHz WAV, and it > would be better to resample to that from another lossles format than > to go raw data > lossy format > WAV. > > Regards > Stephen > > -- Christopher Brooks, BSc, MSc ARIES Laboratory, University of Saskatchewan Web: http://www.cs.usask.ca/~cab938 Phone: 1.306.966.1442 Mail: Advanced Research in Intelligent Educational Systems Laboratory Department of Computer Science University of Saskatchewan 176 Thorvaldson Building 110 Science Place Saskatoon, SK S7N 5C9 ### UNIVERSITY OF CAPE TOWN This e-mail is subject to the UCT ICT policies and e-mail disclaimer published on our website at http://www.uct.ac.za/about/policies/emaildisclaimer/ or obtainable from +27 21 650 9111. This e-mail is intended only for the person(s) to whom it is addressed. If the e-mail has reached you in error, please notify the author. If you are not the intended recipient of the e-mail you may not use, disclose, copy, redirect or print the content. If this e-mail is not related to the business of UCT it is sent by the sender in the sender's individual capacity. ### _______________________________________________ Matterhorn mailing list [email protected] http://lists.opencastproject.org/mailman/listinfo/matterhorn To unsubscribe please email [email protected] _______________________________________________
