【FFmpeg+SDL】播放音频时,声音正常但是有杂音问题(已解决)

下面这个函数是SDL音频的回调函数(修改后的)

void  fill_audio(void *udata,Uint8 *stream,int len)
{
    static int cc = 0;
    cc++;
    qDebug()<<QString::fromLocal8Bit("想要填充:%1字节").arg(len)<<cc;


    AudioOutput* is = static_cast<AudioOutput*>(udata);
    SDL_memset(stream, 0, static_cast<size_t>(len));
    while(len > 0)
    {
        if(is->audio_buf_size == is->audio_buf_readed)   //没有解码后的数据
        {
            AVFrame* frame = is->queue_->Pop(10);
            if(frame)   //获取帧成功
            {
                if(is->swsCtx == nullptr)
                {
                    swr_alloc_set_opts2(&is->swsCtx,&is->dst_tgt_.channel_layout,is->dst_tgt_.fmt,is->dst_tgt_.freq,
                                                    &frame->ch_layout,static_cast<enum AVSampleFormat>(frame->format),frame->sample_rate,0,nullptr);
                    if(is->swsCtx == nullptr || swr_init(is->swsCtx) < 0)
                    {
                        qDebug()<<QString::fromLocal8Bit("重采样初始化失败");
                        swr_free(&is->swsCtx);
                        return;
                    }
                    qDebug()<<QString::fromLocal8Bit("目标数据,%1,%2,%3").arg(is->dst_tgt_.channel_layout.nb_channels)
                              .arg(is->dst_tgt_.fmt).arg(is->dst_tgt_.freq);
                    qDebug()<<QString::fromLocal8Bit("帧数据,%1,%2,%3").arg(frame->ch_layout.nb_channels)
                              .arg(frame->format).arg(frame->sample_rate);
                }
                uint8_t** in = static_cast<uint8_t**>(frame->extended_data);
                uint8_t** out = &is->audio_buf1_;
                int out_samples = frame->nb_samples*is->dst_tgt_.freq/frame->sample_rate;
                int out_bytes = av_samples_get_buffer_size(nullptr,is->dst_tgt_.channels,out_samples,is->dst_tgt_.fmt,0);
                if(out_bytes < 0)
                {
                    qDebug()<<QString::fromLocal8Bit("重采样计数失败");
                    return;
                }
                qDebug()<<QString::fromLocal8Bit("重采样计数成功")<<out_bytes;
                av_fast_malloc(&is->audio_buf1_,&is->audio_buf1_size,static_cast<size_t>(out_bytes));

                int len2 = swr_convert(is->swsCtx,out,out_samples,in,frame->nb_samples);
                qDebug()<<QString::fromLocal8Bit("hhhh:")<<out_samples<<frame->nb_samples <<len2;
                if(len2<0)
                {
                    qDebug()<<QString::fromLocal8Bit("重采样失败");
                    return;
                }
                is->audio_buf_ = is->audio_buf1_;
                is->audio_buf_size = av_samples_get_buffer_size(nullptr,is->dst_tgt_.channels,len2,is->dst_tgt_.fmt,0);
                is->audio_buf_readed=0;


                av_frame_free(&frame);
            }else{  //获取帧失败
                qDebug()<<QString::fromLocal8Bit("获取帧失败");
            }
        }else{
            int len2 = is->audio_buf_size-is->audio_buf_readed;
            len2=(len>len2?len2:len);
            SDL_MixAudio(stream,is->audio_buf_+is->audio_buf_readed,len2,SDL_MIX_MAXVOLUME/4);
            is->audio_buf_readed+=len2;

            len -= len2;
            stream += len2;
        }
    }

}

与修改之前,增加了stream+=len2;

因为这会导致每次填充数据时覆盖同一块内存区域，从而引发音频数据重复、错位，最终表现为杂音。