相关
x264编码
ffmpeg 编码示例
码流控制
h264编解码末尾丢帧
示例
-
编码前初始化，返回视频宽高
int* decode_init(char * in_filename)
{
avcodec_register_all();
av_register_all();
decode_frame = av_frame_alloc();
AVPacket pkt;
//获取各种上下文
if ((ret = avformat_open_input(&ifmt_ctx, in_filename, 0, 0)) < 0) {
retu = -1;
goto end;
}
if ((ret = avformat_find_stream_info(ifmt_ctx, 0)) < 0) {
retu = -2;
goto end;
}
//例遍流，找到流所对应得下标
for (i = 0; i < ifmt_ctx->nb_streams; i++) {
/ /Create output AVStream according to input AVStream
AVFormatContext *ofmt_ctx;
AVStream *in_stream = ifmt_ctx->streams[i];
AVStream *out_stream = NULL;if (ifmt_ctx->streams[i]->codec->codec_type == AVMEDIA_TYPE_VIDEO) { videoindex = i; } } //open decoder video_dec_ctx = ifmt_ctx->streams[videoindex]->codec; video_dec = avcodec_find_decoder(video_dec_ctx->codec_id); if(avcodec_open2(video_dec_ctx,video_dec,NULL)<0) { retu = -3; goto end; } double g_height = ifmt_ctx->streams[videoindex]->codec->height; double g_width = ifmt_ctx->streams[videoindex]->codec->width; int* wh = malloc(sizeof(int)*2); wh[0] = g_width; wh[1] = g_height; end: if(retu != 0) return NULL; else return wh; } -
解码一帧
AVFrame* decode_next()
{
if(decode_frame!=NULL)
av_frame_unref(decode_frame);
int ret = 0;
int got_frame = 0;
int error_time = 0;
while(1)
{
//Get an AVPacket
if (av_read_frame(ifmt_ctx, &pkt) < 0)
{
av_free_packet(&pkt);
goto decode_free;
}
if (pkt.stream_index == videoindex)
{
ret = avcodec_decode_video2(video_dec_ctx,decode_frame, &got_frame, &pkt);
if(got_frame)
goto decode_success;
else
{
if(failed_times ++<30)
continue;
else
goto decode_free;
}
}
av_free_packet(&pkt);
}
decode_free:
av_free_packet(&pkt);
return NULL;decode_success: return decode_frame; }
仅仅是在读取packet之后就停止解码会丢帧，参看
所以要在读取packet失败之后接着调用解码，获取剩余的帧。使用一个变量failed_times 记录编码器中存在的帧数。在读取结束之后接着调用failed_times 次avcodec_decode_video2
int failed_times = 0；
int read_packet_failed = 0;
AVFrame* decode_next()
{
if(decode_frame!=NULL;
av_frame_unref(decode_frame);
int ret = 0;
int got_frame = 0;
int error_time = 0;
while(1)
{
if (av_read_frame(ifmt_ctx, &pkt) < 0)
{
read_packet_failed = 1;
av_free_packet(&pkt);
if(failed_times > 0)
{
failed_times--;
goto decode;
}
else
goto decode_free;
}
if (pkt.stream_index == videoindex)
{
decode:
ret = avcodec_decode_video2(video_dec_ctx,decode_frame, &got_frame, &pkt);
if(got_frame)
goto decode_success;
else
{
if(read_packet_failed)
goto decode_free;
else
{
failed_times ++;
continue;
}
else
goto decode_free;
}
}
av_free_packet(&pkt);
}
decode_free:
av_free_packet(&pkt);
return NULL;
decode_success:
return decode_frame;
}
- 解码完成之后释放
int decode_release() { avcodec_close(video_dec_ctx); avformat_close_input(&ifmt_ctx); if(decode_frame!=NULL) { av_frame_free(&decode_frame); decode_frame = NULL; } }
