On Thursday, July 19, 2018 at 10:25:05 PM UTC-7, [email protected] wrote: > On Thursday, July 19, 2018 at 2:47:13 AM UTC-7, Timothy B. Terriberry wrote: > > raycarino--- via dev-media wrote: > > >>> I'm on firefox 59. My microphone records audio at a sample rate of > > >>> 44.1khz. However, MediaRecorder outputs OGG Opus audio at 48khz. > > >> > > >> This is what you wanted, right? > > > Thank you for the quick reply! > > > > > > Sorry, for the typo. Expected: 48kHz output. Actual is 44.1kHz. It seems > > > that the resampling logic either failed or wasn't reached. > > > > No worries. I figured there was a typo somewhere, just trying to figure > > out exactly where. > > > > The Ogg Opus file format does not actually support encoding 44.1 kHz > > audio directly, so unless you can hear some sort of weird pitch shifting > > going on, that means it hit the resampling logic correctly. > > > > What it does do is store the original sampling rate in the header as > > metadata. That lets other tools resample back to the original sampling > > rate if that is appropriate. E.g., if the input was originally 44.1 kHz, > > it's normal to resample back to 44.1 kHz when decoding to a file to > > avoid surprises for users who don't know that Opus internally only > > supports sample rates that evenly divide 48 kHz. But if you were just > > playing the file back, you'd normally skip that resampling as most > > soundcards run at 48 kHz natively. > > > > I hope that helps! > It does. Thank you so much Timothy and Andreas! > > Re: Andreas' question about how I'm checking the output files. > I was only checking the input sample rate section of the OGG header. I > expected it be the encoded sample rate, but that assumption was wrong and > clarified by Timothy.
I have a follow on question. What's the best way to determine an Ogg Opus file's encoded sample rate? I've tried ffprobe as suggested by Andreas like so: $: ffprobe -show_streams dicto_44.1_label.ogg >>> ... [STREAM] ... sample_rate=48000 ... [/STREAM] Does this ffprobe command prove the file is encoded at 48kHz? In my mind, it's also possible that the [STREAM] section's sample rate could also be the decoding sample rate per the RFC's spec "1. If the hardware supports 48 kHz playback, decode at 48 kHz." https://tools.ietf.org/html/rfc7845#section-5.1. _______________________________________________ dev-media mailing list [email protected] https://lists.mozilla.org/listinfo/dev-media
