static int init_resampler(AVCodecContext *input_codec_context, AVCodecContext *output_codec_context, SwrContext **resample_context) { /** * Only initialize the resampler if it is necessary, i.e., * if and only if the sample formats differ. */ if (input_codec_context->sample_fmt != output_codec_context->sample_fmt || input_codec_context->channels != output_codec_context->channels) { int error; /** * Create a resampler context for the conversion. * Set the conversion parameters. * Default channel layouts based on the number of channels * are assumed for simplicity (they are sometimes not detected * properly by the demuxer and/or decoder). */ *resample_context = swr_alloc_set_opts(NULL, av_get_default_channel_layout(output_codec_context->channels), output_codec_context->sample_fmt, output_codec_context->sample_rate, av_get_default_channel_layout(input_codec_context->channels), input_codec_context->sample_fmt, input_codec_context->sample_rate, 0, NULL); if (!*resample_context) { fprintf(stderr, "Could not allocate resample context\n"); return AVERROR(ENOMEM); } /** * Perform a sanity check so that the number of converted samples is * not greater than the number of samples to be converted. * If the sample rates differ, this case has to be handled differently */ av_assert0(output_codec_context->sample_rate == input_codec_context->sample_rate); /** Open the resampler with the specified parameters. */ if ((error = swr_init(*resample_context)) < 0) { fprintf(stderr, "Could not open resample context\n"); swr_free(resample_context); return error; } } return 0; }