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New to Opus, some questions, newbie
FunkyRes
post Feb 6 2014, 10:19
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I literally started playing with Opus less than 48 hours ago.

So far it is blowing me away.

What I am using it for is speech that currently encoded in MP3 typically at 128 or 192 kbps (a few at 320 !!) - not music, speech. I do not have the original lossless.

These are short clips served via html5 audio, needed vorbis for Opera / Linux browsers. Then I remembered hearing people raving about Opus at low bitrates so I decided to try it.

At --bitrate 16 the file size is so so so much smaller yet it not only sounds acceptable, it sounds spectacular. Clearly this is better way to do speech than MP3 or Vorbis.

Q1) With opusenc I tried using the --comment COVERARTMIME="image/png" and --comment COVERART="base64 of art" but even with the art as small as 320x320, opusenc dies on me complaining arguments too long. Is there a way to add cover art? I tried using vorbiscomment to modify the tags after encoding but it doesn't like opus. Not really a big deal, but it's nice for there to be cover art when possible.

//this is more icecast more than opus related
Q2) May be setting up an icecast server and serve the stream with opus. Not just these speech files, but also music fils. Most of these files are mono, music is stereo. With that possibility in mind, should I be encoding them as stereo or does icecast smoothly switch between mono and stereo opus inputs?

Q3) Some of the source files were recorded at low sample rates, being just speech I guess they just figured they didn't need the file size of 44.1 kHz sample rates when they recorded it. opusenc looks like it resamples to 48 kHz which is fine by me, is that really what it is doing? Or will decoding switch it back to those odd sample rates?

What am asking is if I need to resample the audio with sox after mp3 decode before sending it to opusenc or if opusenc does that for me. I believe these weird sample rates have caused issues when these files have been streamed via live365 but I don't do that so I don't really know. But if the icecast route becomes a reallity then I'd have to re-encode to fix sample rate.

Q4) I've seen there is Windows support via a DirectShow plugin. Does that plugin work with HTML5 Audio or is it like Ogg Vorbis where the plugin works in most things but not IE with HTML5 audio? Sorry, not a Windows guy.

Thanks if any of those questions can be answered.
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FunkyRes
post Feb 6 2014, 10:24
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Ah just this -

http://www.hydrogenaudio.org/forums/index....showtopic=97051

So it looks like it will be decoded at 48 kHz and I don't have to worry about resampling before feeding it to opusenc. Not for sample frequency anyway.
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Mangix
post Feb 7 2014, 06:12
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Q1: I use foobar2000 to add cover art to everything. This is windows specific and probably not what you are looking for. Although foobar2000 does run pretty well in Wine.

Q4: LAV Filters support Opus just fine: http://forum.doom9.org/showthread.php?t=156191 DirectShow is in no way related to web browsers. If you want IE11 support, you'd probably need to find a flash applet which decodes Opus.

This post has been edited by Mangix: Feb 7 2014, 06:13
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jmvalin
post Feb 7 2014, 09:22
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QUOTE (FunkyRes @ Feb 6 2014, 04:19) *
Q4) I've seen there is Windows support via a DirectShow plugin. Does that plugin work with HTML5 Audio or is it like Ogg Vorbis where the plugin works in most things but not IE with HTML5 audio? Sorry, not a Windows guy.


HTML5 audio tag with Opus has been supported in Firefox for a while now and I believe that Chrome and Opera now has support by default (otherwise it's a switch that needs to be turned on).
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FunkyRes
post Feb 7 2014, 11:33
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QUOTE (Mangix @ Feb 6 2014, 21:12) *
Q1: I use foobar2000 to add cover art to everything. This is windows specific and probably not what you are looking for. Although foobar2000 does run pretty well in Wine.

Q4: LAV Filters support Opus just fine: http://forum.doom9.org/showthread.php?t=156191 DirectShow is in no way related to web browsers. If you want IE11 support, you'd probably need to find a flash applet which decodes Opus.


Actually it is DirectShow filters that allow IE html5 to support WebM (but they internal blacklist ogg vorbis audio, putting vorbis in mkv though allegedly works)

That would be interesting to try - put opus in mkv and see if it works, that would indicate it is audio/ogg mimetype they blacklist (which I suspect)
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Miramis
post Feb 7 2014, 14:16
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QUOTE (jmvalin @ Feb 7 2014, 09:22) *
HTML5 audio tag with Opus has been supported in Firefox for a while now and I believe that Chrome and Opera now has support by default (otherwise it's a switch that needs to be turned on).

Enabled by default in Chromium 33 (Revision 235337).


--------------------
Rhythmbox, Flac + Vorbis, Sennheiser HD650 + Sony MDR-XB1000
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