我自己解码的时候遇到点问题,暂时先占位。后面若搞定了,再添加。
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// 2014/3/9 -- 19:24更新
FILE *pFile; pFile = fopen("wavinflag.pcm", "wb"); while( av_read_frame(pFormatCtx, packet) >= 0 ) { if( packet->stream_index == audioStream ) { int got_picture; int ret = avcodec_decode_audio4( audioCodecCtx, audioFrame, &got_picture, packet); if( ret < 0 ) { printf("Error in decoding audio frame.\n"); exit(0); } if( got_picture ) { int in_samples = audioFrame->nb_samples; short *sample_buffer = (short*)malloc(audioFrame->nb_samples * 2 * 2); memset(sample_buffer, 0, audioFrame->nb_samples * 4); printf("in_samples = %d\n", in_samples); int i=0; float *inputChannel0 = (float*)(audioFrame->extended_data[0]); // Mono if( audioFrame->channels == 1 ) { for( i=0; i<in_samples; i++ ) { float sample = *inputChannel0++; if( sample < -1.0f ) { sample = -1.0f; } else if( sample > 1.0f ) { sample = 1.0f; } sample_buffer[i] = (int16_t)(sample * 32767.0f); } } else { // Stereo float* inputChannel1 = (float*)(audioFrame->extended_data[1]); for( i=0; i<in_samples; i++) { sample_buffer[i*2] = (int16_t)((*inputChannel0++) * 32767.0f); sample_buffer[i*2+1] = (int16_t)((*inputChannel1++) * 32767.0f); } } fwrite(sample_buffer, 2, in_samples*2, pFile); } } // Free the packet that was allocated by av_read_frame av_free_packet(packet); }
在使用ffmpeg解码aac的时候,如果使用avcodec_decode_audio4函数解码,那么解码出来的会是AV_SAMPLE_FMT_FLTP 格式的数据( float, 4bit , planar), 如果我们希望得到16bit的数据(如AV_SAMPLE_FMT_S16P数据),那么我们需要转换一下:
解決方式:这里SDL2.0播放pcm有点问题,还没弄会。
将FLTP转为S16代码,详细代码这里下载。