ffmpeg avcodec_encode_video2 前面10多帧不能实时编码

ffmpeg avcodec_encode_video2 前面10多帧不能实时编码，查找原因！版本v1.2.1

 

原因找到：需要设置编码的速度和是否实时编码；见红色的部分！

 

注意：

 #include <libavutil/opt.h>

 

/* Add an output stream. */
static AVStream *add_stream(AVFormatContext *oc, AVCodec **codec,
       enum AVCodecID codec_id)
{
 AVCodecContext *c;
 AVStream *st;

 /* find the encoder */
 *codec = avcodec_find_encoder(codec_id);
 if (!(*codec)) {
  fprintf(stderr, "Could not find encoder for '%s'\n",
   avcodec_get_name(codec_id));
  exit(1);
 }

 st = avformat_new_stream(oc, *codec);
 if (!st) {
  fprintf(stderr, "Could not allocate stream\n");
  exit(1);
 }
 st->id = oc->nb_streams-1;
 c = st->codec;

 switch ((*codec)->type) {
 case AVMEDIA_TYPE_AUDIO:
  st->id = 1;
  c->sample_fmt  = AV_SAMPLE_FMT_S16;
  c->bit_rate    = 64000;
  c->sample_rate = 44100;
  c->channels    = 2;
  break;

 case AVMEDIA_TYPE_VIDEO:
  c->codec_id = codec_id;

  c->bit_rate = 400000;
  /* Resolution must be a multiple of two. */
  c->width    = 352;
  c->height   = 288;
  /* timebase: This is the fundamental unit of time (in seconds) in terms
  * of which frame timestamps are represented. For fixed-fps content,
  * timebase should be 1/framerate and timestamp increments should be
  * identical to 1. */
  c->time_base.den = STREAM_FRAME_RATE;
  c->time_base.num = 1;
  c->gop_size      = 12; /* emit one intra frame every twelve frames at most */
  c->pix_fmt       = STREAM_PIX_FMT;
  if (c->codec_id == AV_CODEC_ID_MPEG2VIDEO) {
   /* just for testing, we also add B frames */
   c->max_b_frames = 2;
  }
  if (c->codec_id == AV_CODEC_ID_MPEG1VIDEO) {
   /* Needed to avoid using macroblocks in which some coeffs overflow.
   * This does not happen with normal video, it just happens here as
   * the motion of the chroma plane does not match the luma plane. */
   c->mb_decision = 2;
  }

  //防止编码延迟修改参数
  av_opt_set(c->priv_data, "preset", "superfast", 0); 
  av_opt_set(c->priv_data, "tune", "zerolatency", 0);

  break;

 default:
  break;
 }

 /* Some formats want stream headers to be separate. */
 if (oc->oformat->flags & AVFMT_GLOBALHEADER)
  c->flags |= CODEC_FLAG_GLOBAL_HEADER;

 return st;
}

 

修改后的例子见：

http://blog.youkuaiyun.com/smilestone_322/article/details/17002575