FFmpeg编程学习笔记二：音频重采样

标签：ffmpeg   编程   学习笔记   音频重采样   

      ffmpeg实现音频重采样的核心函数swr_convert功能非常强大，可是ffmpeg文档对它的注释太过简单，在应用中往往会出这样那样的问题，其实在读取数据->重采样->编码数据的循环中在第一次执行swr_convert后还应用swr_convert再作个缓存检测看看是否还有数据，如果有就要把它写到FIFO中去，留在下次再使用，这点在转码和由低向高转换采样率时特别重要。

     下面一段简单的代码，摘自我自已写的测试程序.

	const int frame_size = FFMIN(fifo_size, m_Opt->encode_pCodecCtx->frame_size);


	if ((ret = av_audio_fifo_read(m_fifo, (void **)m_fifo_samples_array, frame_size)) < frame_size) {
		fprintf(stderr, "Could not read data from FIFO\n");
		return AVERROR_EXIT;
	}

	int out_samples = av_rescale_rnd(swr_get_delay(m_Opt->out_resample_context, 48000) + 1536, 44100, 48000, AV_ROUND_UP);


	int conver_samples= swr_convert(m_Opt->out_resample_context, m_fifo_conver_samples_array, frame_size,
		(const uint8_t **)m_fifo_samples_array, frame_size);
	ret = av_audio_fifo_size(m_conver_fifo);

	if ((ret = av_audio_fifo_realloc(m_conver_fifo, av_audio_fifo_size(m_conver_fifo) + frame_size)) < 0) {
			fprintf(stderr, "Could not reallocate FIFO\n");
			return ret;
		}

	ret = av_audio_fifo_write(m_conver_fifo, (void **)m_fifo_conver_samples_array, conver_samples);
		fifo_size = av_audio_fifo_size(m_conver_fifo);

		if ((ret = av_audio_fifo_read(m_conver_fifo, (void **)m_Opt->out_samples_array, frame_size)) < frame_size) {
			fprintf(stderr, "Could not read data from FIFO\n");
			return AVERROR_EXIT;
		}
		
		ret = Encode_audio(ret);

		int ret1 = 0;

		while ((ret1 = swr_convert(m_Opt->out_resample_context, m_fifo_conver_samples_array, frame_size, NULL, 0)) > 0)
	{
	

		if ((ret = av_audio_fifo_realloc(m_conver_fifo, av_audio_fifo_size(m_conver_fifo) + ret1)) < 0) {
			fprintf(stderr, "Could not reallocate FIFO\n");
			return ret;
		}

		ret = av_audio_fifo_write(m_conver_fifo, (void **)m_fifo_conver_samples_array, ret1);
		fifo_size = av_audio_fifo_size(m_conver_fifo);

		if (fifo_size > m_Opt->encode_pFrame->nb_samples)
		{

			if ((ret = av_audio_fifo_read(m_conver_fifo, (void **)m_Opt->out_samples_array, frame_size)) < frame_size) {
				fprintf(stderr, "Could not read data from FIFO\n");
				return AVERROR_EXIT;
			}

			ret = Encode_audio(ret);

		}

FFmpeg编程学习笔记二：音频重采样

标签：ffmpeg   编程   学习笔记   音频重采样   

原文地址：http://blog.csdn.net/qsq3/article/details/47049139