FFMPEG api转换文件错误

多亏了API，我才尝试转换视频。我对API进行了一些修改（比如5行），并强制编解码器使用

MJPEG

。它编码3或4帧，然后停止说

无效的pts（3）
Input #0, mov,mp4,m4a,3gp,3g2,mj2, from '/Users/thomas/test.mov':
  Metadata:
    major_brand     : qt  
    minor_version   : 0
    compatible_brands: qt  
    creation_time   : 2014-09-05 15:42:24
  Duration: 00:00:29.70, start: 0.000000, bitrate: 943 kb/s
    Stream #0:0(und): Video: h264 (High) (avc1 / 0x31637661), yuv420p(tv, bt709), 1280x720, 935 kb/s, SAR 1:1 DAR 16:9, 60 fps, 60 tbr, 6k tbn, 50 tbc (default)
    Metadata:
      creation_time   : 2014-09-05 15:42:24
      handler_name    : Core Media Data Handler
      encoder         : H.264
      timecode        : 00:00:00:00
    Stream #0:1(und): Data: none (tmcd / 0x64636D74), 0 kb/s (default)
    Metadata:
      creation_time   : 2014-09-05 15:42:24
      handler_name    : Core Media Data Handler
      timecode        : 00:00:00:00
Output #0, mov, to '/Users/thomas/test_MJPEG.mov':
    Stream #0:0: Video: mjpeg, yuvj420p, 1280x720, q=2-31, 128 kb/s, 50 tbc
    Stream #0:1: Data: none (tmcd / 0x64636D74), 0 kb/s
[mov @ 0x7ffd6202e600] Using AVStream.codec.time_base as a timebase hint to the muxer is deprecated. Set AVStream.time_base instead.
[mov @ 0x7ffd6202e600] Using AVStream.codec.time_base as a timebase hint to the muxer is deprecated. Set AVStream.time_base instead.
[swscaler @ 0x7ffd6204d000] deprecated pixel format used, make sure you did set range correctly
Pushing decoded frame to filters
Pulling filtered frame from filters
Encoding frame
Pulling filtered frame from filters
Pushing decoded frame to filters
Pulling filtered frame from filters
Encoding frame
Pulling filtered frame from filters
Pushing decoded frame to filters
Pulling filtered frame from filters
Encoding frame
Pulling filtered frame from filters
Pushing decoded frame to filters
Pulling filtered frame from filters
Encoding frame
Pulling filtered frame from filters
Pushing decoded frame to filters
Pulling filtered frame from filters
Encoding frame
[mjpeg @ 0x7ffd6202ec00] Invalid pts (3) <= last (3)
Error occurred: Operation not permitted