lame音频编码注意的点
1.注意每次编码的PCM数据不能太短,如果太短编码函数长期返回-1这样的错误,将导致编码器彻底失效程序奔溃的问题,经测试32000在3200下稳定,大概1/10码率是没有问题的,具体请自行查询或调试
/* * input pcm data, output (maybe) mp3 frames. * This routine handles all buffering, resampling and filtering for you. * * return code number of bytes output in mp3buf. Can be 0 * -1: mp3buf was too small * -2: malloc() problem * -3: lame_init_params() not called * -4: psycho acoustic problems * * The required mp3buf_size can be computed from num_samples, * samplerate and encoding rate, but here is a worst case estimate: * * mp3buf_size in bytes = 1.25*num_samples + 7200 * * I think a tighter bound could be: (mt, March 2000) * MPEG1: * num_samples*(bitrate/8)/samplerate + 4*1152*(bitrate/8)/samplerate + 512 * MPEG2: * num_samples*(bitrate/8)/samplerate + 4*576*(bitrate/8)/samplerate + 256 * * but test first if you use that! * * set mp3buf_size = 0 and LAME will not check if mp3buf_size is * large enough. * * NOTE: * if gfp->num_channels=2, but gfp->mode = 3 (mono), the L & R channels * will be averaged into the L channel before encoding only the L channel * This will overwrite the data in buffer_l[] and buffer_r[]. * */
2.针对PCM数据选择正确的编码方法
// mp3 encode //整形short类型PCM数据 int recvLen = lame_encode_buffer(_lame, recordingData, recordingData, nsamples, buffer, pcmLen); //浮点类型PCM数据 int recvLen = lame_encode_buffer_interleaved_ieee_float(_lame, recordingData, nsamples, buffer, pcmLen); //浮点类型PCM数据 int recvLen = lame_encode_buffer_ieee_float(_lame, recordingData, recordingData, nsamples, buffer, pcmLen);