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Topic: Foobar OPUS decoding (Read 746 times) previous topic - next topic
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Foobar OPUS decoding

While transcoding some OPUS files to WAV using Foobar v1.5.1, I noticed that portions of the audio on the output file were clipped.
The clipping does not occur when using the official opus-tools software to transcode the same OPUS files to WAV. 
It would appear that Foobar is adding gain during the decoding process, but I have replaygain and all other processing (DSPs) disabled.

Attached is an image showing a portion of the resulting WAV files. At the top is (one channel of) the output from Foobar. Below is the equivalent output from opus-tools, inverted to make a visual comparison easier.

Am I missing something?


Re: Foobar OPUS decoding

Reply #1
Did you somehow have foo_input_vgmstream high in your decoder priority list? That component also supports Opus, mainly to support random game formats, and outputs everything as 16 bit, clipped obviously.

Re: Foobar OPUS decoding

Reply #2
I think you got it backwards. opusdec from opus-tools applies the opus header gain when decoding.

Re: Foobar OPUS decoding

Reply #3
No foo_input_vgmstream in my decoder priority list.
I don't have it backwards - foobar's output has the clipping.
"Opus header gain" is 0.00dB, as confirmed in fb2k's file properties window.

Thanks for the suggestions thus far.

Re: Foobar OPUS decoding

Reply #4
It will be clipping if you convert to 16 or 24 bit format WAV file. Are you converting to 32 bit?

Re: Foobar OPUS decoding

Reply #5
No I'm not converting to 32-bit, or between other bit depths  (but why should that create clipping anyway?)
It's just 16-bit 48k input, 16-bit 48k output.

Re: Foobar OPUS decoding

Reply #6
It's just 16-bit 48k input,
Opus (and many other lossy formats such as MP3, AAC or Vorbis) doesn't have bit depth.

Back to the question: Opus decoder has "soft clipping" feature. You can achieve similar results with foobar2000: add "Advanced Limiter" to the Active DSPs list.


Re: Foobar OPUS decoding

Reply #7
You have to convert to 32-bit floating point output if you want no clipping of the signal, or use a DSP which alleviates the effects of clipping, since lossy codecs like this will introduce clipping all on their own.

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