[Libav-user] I can't get audio decoding to work.

[Bill Messenger]

Update: I found out that it only crashes in debug mode. When I build it in
release mode, it doesn't crash. It must be a bug in MSVC 2015 or something.

On Fri, Jun 17, 2016 at 4:06 PM, Bill Messenger <apothemmusic at gmail.com>
wrote:

> I'm trying to create a class that uses FFmpeg to decode any audio file and
> store it into memory. Then it has a function that returns a float value of
> any sample in that buffer. The code I wrote works perfectly for wav and
> flac files, produces weird audio for mp3 and ogg files, and crashes on
> certain mp3 files. I spent days trying to figure out why it isn't working,
> but I can't come up with anything.
>
> I think the reason why the audio is weird for mp3 and ogg files is that it
> uses planar audio instead of interleaved audio, but I don't see what's
> wrong with the code I wrote. I may be missing something though. For
> example, to get a sample for 16 bit interleaved audio I use:
>
> int16_t tmp = ((int16_t*)sampleBuffer)[numChannels*sample + channel];
> rv = (float)tmp / 32767.0f;
>
> and to get a sample for 16 bit planar audio I use:
>
> int16_t tmp = ((int16_t*)sampleBuffer)[sample + numSamples*channel];
> rv = (float)tmp / 32767.0f;
>
> And I have no clue why it crashes on certain mp3 files. I paid close
> attention to make sure there is enough memory allocated in the buffer.
> What's even weirder is that the file I created "Chiptune 15 2.mp3" didn't
> crash, but when I renamed it to "test.mp3", it crashed! These crashes
> happen on line 139 of "AudioDecoder.cpp":
>
> std::memcpy(sampleBuffer + totalBufferSize, frame->extended_data[0],
> dataSize);
>
> with an "Access violation reading location" error in vcruntime140d.dll. It
> says it isn't with location 0x0000000000000000 or 0xFFFFFFFFFFFFFFFF
> though, it's a different random location.
>
> I attached a zip file with the c++ code and two mp3's. Oh yeah, I should
> also mention that I'm using MSVC 2015 Community in Windows 10.
>
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