[Libav-user] How to read in planar data?

[Paul B Mahol]

On 12/6/19, Mark McKay <mark at kitfox.com> wrote:
> I'm having trouble trying to figure out how to read in planar data.  I
> have a file that has data in the AV_SAMPLE_FMT_FLTP format with two
> channels.  Below is my attempt to read in the data.  This will crash
> with a memory problem if I try to read in the second channel (but it
> will complete if I bypass the second and just read from channel 0).  Am
> I doing this right?
>
> void AudioReader::loadAudioFrame(AVPacket& packet)
> {
> int err = avcodec_send_packet(aCodecCtx, &packet);
> if (err < 0)
> {
> qDebug("Error sending packet to decoder");
> return;
> }
>
> int numChannels = aCodecCtx->channels;
> while (err >= 0)
> {
> err = avcodec_receive_frame(aCodecCtx, aFrame);
> if (err == AVERROR(EAGAIN) || err == AVERROR_EOF)
> return;
>
> if (err < 0)
> {
> qDebug() << "Error decoding packet: " << err;
> return;
> }
>
> int bytesPerSample = av_get_bytes_per_sample(aCodecCtx->sample_fmt);
> if (bytesPerSample < 0) {
> /* This should not occur, checking just for paranoia */
> fprintf(stderr, "Failed to calculate data size\n");
> exit(1);
> }
>
> int bufferSize = av_samples_get_buffer_size(NULL,
> aCodecCtx->channels,
> aFrame->nb_samples,
> aCodecCtx->sample_fmt,
> 1);
>
> switch(aCodecCtx->sample_fmt)
> {
> ...
> case AV_SAMPLE_FMT_FLTP:
> {
> //Serial format - change to interleaved order
> for (int i = 0; i < aFrame->nb_samples; i++)
> {
> for (int ch = 0; ch < numChannels; ch++)
> {
> _audioBytes.append((const char *)aFrame->data[ch] + i * sizeof(float),
> sizeof(float));
> }
> }
> break;
> }
> }
> }

Use valgrind to point to exact position in your code that triggers crash.

>
> ---
> http://www.kitfox.com