ffmpeg转码和转文件总结（MP3-->aac）

来源：互联网发布：windows密钥能用几次编辑：程序博客网时间：2024/05/23 05:09

视频遇到的错误

1、设置帧率

video_st->time_base.num = 1;

video_st->time_base.den = 25;

如果还不管用：

AVDictionary* opt = NULL;
av_dict_set(&opt, "video_track_timescale", "25", 0);
if (avformat_write_header(oc,&opt)<0)
{
fprintf(stderr, "Could not write header for output file\n");
exit(1);
}

2、提示错误 //[mp4 @ 02d07fe0] Codec for stream 0 does not use global headers but container format requires global header

解决方法：

//oVcc->flags = CODEC_FLAG_GLOBAL_HEADER;
if(oc->oformat->flags & AVFMT_GLOBALHEADER)
oVcc->flags |= CODEC_FLAG_GLOBAL_HEADER;

3、h264需要设置的参数

oVcc->qmin = 10;
oVcc->qmax = 51;

//设置参数
AVDictionary *param = 0;
if (oVcc->codec_id == AV_CODEC_ID_H264)
{
av_dict_set(&param, "preset", "superfast",0);
av_dict_set(&param, "tune", "zerolatency",0);
}

oVc = avcodec_find_encoder(oVcc->codec_id); //AV_CODEC_ID_H264
if (!oVc){
printf("can't find suitable videoencoder\n");
exit(0);
}
ret = avcodec_open2(oVcc, oVc, &param);
if (ret < 0){
printf("can't open the output video codec\n");
exit(0);
}

4、需要转换pix_fmt

struct SwsContext *img_convert_ctx;
img_convert_ctx = sws_getContext(vCodecCtx->width, vCodecCtx->height, vCodecCtx->pix_fmt,
oVcc->width, oVcc->height, oVcc->pix_fmt, SWS_BICUBIC, NULL, NULL, NULL);

音频错误：

1、需要设置 sample_fmt, 否则解码提示 -22

audio_st->codec->sample_fmt = AV_SAMPLE_FMT_S16; //解码失败 -22 -------------------------------------------

2、

//av_get_channel_layout_nb_channels(channel_layout);
//av_get_default_channel_layout(pCodecCtx->channels);
oAcc->channels = aCodecCtx->channels;
oAcc->channel_layout = aCodecCtx->channel_layout;

3、需要每帧视频的采样数不同，mp3 是1152

int samplesPerFrame = 1024;
if (oAcc->codec_id == AV_CODEC_ID_AAC){
samplesPerFrame = 1024;
}
else if(oAcc->codec_id == AV_CODEC_ID_MP3){
samplesPerFrame = 1152;
}

4、需要转换

struct SwrContext *au_convert_ctx;
au_convert_ctx = swr_alloc();
au_convert_ctx=swr_alloc_set_opts(au_convert_ctx,oAcc->channel_layout, audio_st->codec->sample_fmt, oAcc->sample_rate,
aCodecCtx->channel_layout,aCodecCtx->sample_fmt , aCodecCtx->sample_rate,0, NULL);
swr_init(au_convert_ctx);

//解码得到的数据类型为float 4bit，而播放器播放的格式一般为S16（signed 16bit）,就需要对解码得到的数据进行转换
/data转 extended_data //里面存放着指向数据的指针,下面的红位置
int len = swr_convert(au_convert_ctx,&out_buffer_audio, MAX_AUDIO_FRAME_SIZE,(const uint8_t **)oAFrame->extended_data, oAFrame->nb_samples);

5、1152--》1024 解码出来的AVFrame中的nb_samples 太多，encode 成AAC的时候，会出现 more samples to frame

需要用到 AVAudioFifo 接口

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