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Topic: Encoding podcasts with Opus (Read 2410 times) previous topic - next topic
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Encoding podcasts with Opus

I've been working on finding a suitable codec for re-encoding some podcasts. The source files are mostly >192 kbps in various lossy formats (a few lossless), and the files include mostly speech but also have sound effects, music, that sort of thing.

Lately, I've been doing some ABX testing with foobar2000. The desired bit rate for me would be in the 32 kbps range (maybe up to 48 kbps if the gains are worth it). The contenders for codecs were HE-AAC v2 (Winamp FhG) VBR, HE-AAC CVBR (Apple), Ogg Vorbis, and Opus (libopus 1.2 alpha). I could fairly reliably tell the difference between each at around 32 kbps (I can post the results of the ABX tests later if needed; I'm at work now).

I'm leaning toward Opus but it seems like it's a trade-off. The stereo separation for Opus blew HE-AAC v2 away, and the higher frequencies of the HE-AAC v2 seemed more harsh to my ears than Opus did. However, it seemed like the lower/mid-range frequencies had some noticeable but not terribly annoying artifacts in the Opus encoded file that the HE-AAC v2 did not have.

I've done a lot of reading of various threads on this forum, and what I'm still confused about are Opus' speech vs music modes. Is there something I can do to play around with those modes? And if so, what would be better for a podcast-type file that contains passages of speech AND music? Is Opus the right codec for this sort of task? Any other suggestions?

Re: Encoding podcasts with Opus

Reply #1
No idea how hot podcast are in mobile, but http://caniuse.com/#search=opus (still bad android/ios support as it seems). edit: But I guess there might be specific podcast apps/players there, not browser related.
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Re: Encoding podcasts with Opus

Reply #2
I suppose I should clarify that these podcasts are not for publication, they are for my own personal listening. I will be using Poweramp for Android (I only have version 2 at the moment but I believe the current alpha release of version 3 supports Opus).

Re: Encoding podcasts with Opus

Reply #3
It would be easier to just buy a larger SD card and leave things as they are.

Re: Encoding podcasts with Opus

Reply #4
It would be easier to just buy a larger SD card and leave things as they are.

Well, sure, but you could say that about lots of things. I'd rather make the most efficient use of the space I have.

Anyway, I did some more ABX testing and I think I've settled on Opus @ 48 kbps. The channel separation and bandwidth at that bit rate is good enough to not be too annoying for the music/effects bits (for me) and the speech bits are nearly transparent. None of the other codecs I tried came close. I'm impressed with Opus so far.

 

Re: Encoding podcasts with Opus

Reply #5
Hi, Saucerful

it seemed like the lower/mid-range frequencies had some noticeable but not terribly annoying artifacts in the Opus encoded file
There are new experimental Opus 1.2-alpha builds which address the issue You describe.
https://hydrogenaud.io/index.php/topic,111798.msg933785.html#msg933785

You can try and post your experience in a topic above
https://jmvalin.ca/misc_stuff/opus-tools-buildC.zip
https://jmvalin.ca/misc_stuff/opus-tools-buildD.zip
https://jmvalin.ca/misc_stuff/opus-tools-buildE.zip

Opus 1.2 is getting excellent. I really like what I hear in last 2-3 months.

 
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