In a previous entry discussing YouTube audio I mentioned that Google/YouTube changes the details of their upload formats, transcoding, and streams without much fanfare. Happily all the changes I’ve seen so far have been toward higher quality, and lately they’ve upgraded the audio streams again.
I recently uploaded a set of clips from our guitar party, encoded as 720p/30 H.264 video and PCM 48khz/16 bit audio. When I pulled one of the 720 streams down from YouTube and examined the specs with Mediainfo I discovered that audio is now returned as a 192 kbps AAC stream. This is generally considered to be the audible equivalent of an uncompressed file for nearly all material. In other words, this level of compression using this codec should sound just like the original uncompressed file.
ABX for the Answer
I still strongly believe that any audio comparison should start with an ABX session, to confirm that differences are really being heard. I have observed in myself and others that even blinded, we quickly attach characteristics to a label, and once this happens we “hear” the label as much as the clip, or more.
In order to provide an accurate comparison between the uploaded and downloaded versions, I opened both clips in REAPER. I created a very brief extract of each file along with the full file, each rendered as an uncompressed 44.1/16 WAV file. Be sure to download these clips to listen to them, since they’re .WAV they are not intended for streaming.
So can you do 16 comparisons between these files in a double blind comparison and identify them correctly 13 or more times out of 16? Please let me know in the comments and I’ll get back to you with the ID of the clips.
Some Outside Sources
Google/YouTube has provided a bit of updated and expanded information on file formats, with specific instructions for some common video tools, recommended formats and specs, and so on. Check out the Video encoding page.
A gentleman named Nick Vogt blogs about various tech topics, and has a nice set of charts showing the progress of YouTube audio on this page. His work shows consistent progress from the bad old days of gritty lofi to today’s commercial release quality.
This entry was posted on Thursday, October 4th, 2012 at 6:51 pm and is filed under Recording, Video. You can follow any responses to this entry through the RSS 2.0 feed. You can leave a response, or trackback from your own site.