On 09/04/2013 09:20 AM, Armin Trattnig wrote:
Hello,
I have a question:
The comments in samplefmt.h say that the linesize for a planar format is
in linesize[0] and the same for all used planes.
So if i decode an audiostream and the sampleFormat is AV_SAMPLE_FMT_FLTP
and its stereo and the first AVFrame says
that there are 1024 samples decoded (nb_samples). In my understanding
the bytes per sample is 4 and the first two planes of data are used. So
linesize[0] must be 1024*4 = 4096. But when i decode an AV_CODEC_ID_AAC
the linesize[0] is set to 8192, which would be the total size of used
planes in data. I tried the same with and AV_CODEC_ID_AC3 stream and
there the linesize[0] is correctly set to 6144 after nb_samples = 1536.
Both streams have AV_SAMPLE_FMT_FLTP and are stereo.
AVFrame.linesize[0] for audio is the size of the buffer for one plane.
It does not necessarily mean that the whole buffer contains real audio
samples. For example, it could be padded to a multiple of some specific
size for SIMD processing, or the decoder could buffer more samples than
are needed because it needs the buffer before it knows exactly how many
samples will end up in the frame.
-Justin
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