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FDK AAC vs Opus
birdie
post Nov 13 2013, 10:20
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Accoring to a recent HA test, Opus has beaten all other codecs at 64Kbit, however I've got very different results. I don't know how it's possible but I've just compared Opus 1.0.3 vs Fraunhofer Aac encoder at 64Kb and 48Kb, and Fraunhofer won by a huge margin.

With Fraunhofer I don't hear any discernible audio distortions at 64Kbit and minor disturbances at 48Kbit whereas with Opus the resulting audio has a very low quality. As a test I compressed some pop music songs (relatively simple audio).

CODE
ffmpeg -i source.wav -c:audio libfdk_aac -profile:a aac_he_v2 -ab 48k output.m4a (or aac_he_v1)


For opus I've used:

CODE
-c:a libopus -b:a 64k (or 48k)


Components versions:

ffmpeg version 2.1
fdk-aac-0.1.2
opus-1.0.3

This post has been edited by birdie: Nov 13 2013, 10:27
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Kohlrabi
post Nov 13 2013, 10:23
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Did you perform a (double) blind test?


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birdie
post Nov 13 2013, 10:27
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No, I haven't, the differences in the output can be easily heard.

To give you an example, AAC at 64Kbit sounds more or less like CD audio, Opus at the same bitrate sounds like MP3 at 80Kbit/sec.

Again, maybe Opus 1.1 has improved in regard to low bitrates, but I tested 1.0.3 release.
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Kohlrabi
post Nov 13 2013, 11:46
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QUOTE (birdie @ Nov 13 2013, 11:27) *
AAC at 64Kbit sounds more or less like CD audio, Opus at the same bitrate sounds like MP3 at 80Kbit/sec.
And MP3 at 80kbps does not "sound more or less like CD audio"? That's why anecdotes are not useful and we prefer blind tests. Do you mind posting your samples, the original file and your encodes, so that we have a common ground for discussion? Maybe both encodes have artifacts, but you tend to prefer the AAC ones, but most other users don't.

This post has been edited by Kohlrabi: Nov 13 2013, 11:48


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LithosZA
post Nov 13 2013, 12:20
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You might also want to try out opus-tools instead of libopus in ffmpeg. It might not be using 20ms frames in ffmpeg.

I also briefly tested (with some 1.1 alpha/beta version) @64Kbps a while back and to me each song I tried Opus sounded slightly less annoying than fdk-aac.
@48Kbps fdk-aac sounded better. I don't have any ABX results.
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eahm
post Nov 13 2013, 15:29
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birdie, I too believe AAC is better than Opus but I didn't test and prove it so I won't post anything in regard. All the test that hundreds of people have done say the contrary.

Second, why do you want to test an old version of the codec? Go test 1.1, post one or few logs and tell where you notice the difference if you want people to take you seriously.

This post has been edited by eahm: Nov 13 2013, 15:29


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jmvalin
post Nov 13 2013, 15:44
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QUOTE (LithosZA @ Nov 13 2013, 06:20) *
You might also want to try out opus-tools instead of libopus in ffmpeg. It might not be using 20ms frames in ffmpeg.


Indeed, ffmpeg uses 10 ms frames for Opus. We do not know why they're doing this, but it's sub-optimal. You can get higher quality with 20 ms frames.
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LithosZA
post Nov 16 2013, 14:43
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QUOTE
Indeed, ffmpeg uses 10 ms frames for Opus. We do not know why they're doing this, but it's sub-optimal. You can get higher quality with 20 ms frames.


Is there already a bug logged for this at ffmpeg? I'm struggling to find anything on the ffmpeg bug list.
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Ajaja
post Nov 27 2013, 12:55
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QUOTE (LithosZA @ Nov 16 2013, 15:43) *
QUOTE
Indeed, ffmpeg uses 10 ms frames for Opus. We do not know why they're doing this, but it's sub-optimal. You can get higher quality with 20 ms frames.


Is there already a bug logged for this at ffmpeg? I'm struggling to find anything on the ffmpeg bug list.


I tested latest ffmpeg from git compilied with libopus v1.1-rc. It uses 20ms frames:
CODE
D:\>ffmpeg.exe -i test.wav -c opus test.opus
....
D:\>opusinfo.exe test.opus
Processing file "test.opus"...

New logical stream (#1, serial: f68e8976): type opus
Encoded with Lavf55.21.102
User comments section follows...
        encoder=Lavf55.21.102
Opus stream 1:
        Pre-skip: 312
        Playback gain: 0 dB
        Channels: 2
        Original sample rate: 48000Hz
        Packet duration:   20.0ms (max),   20.0ms (avg),   20.0ms (min)
        Page duration:   1000.0ms (max),  997.1ms (avg),  120.0ms (min)
        Total data length: 3778579 bytes (overhead: 0.728%)
        Playback length: 5m:06.102s
        Average bitrate: 98.75 kb/s, w/o overhead: 98.03 kb/s
Logical stream 1 ended


This post has been edited by Ajaja: Nov 27 2013, 12:56
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LithosZA
post Nov 27 2013, 12:57
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QUOTE
I tested latest ffmpeg from git builded with libopus v1.1-rc. It uses 20ms frames...


Awesome
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