下面这个函数是SDL音频的回调函数(修改后的)
cpp
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。