title: iOS: AVPlayer shows black screen and can't play some mp4 videos
body: <p>I am using AVPlayer in AVFoundation to play mp4 videos in my app. Mostly the player is ok. But these two days i meet a .mp4 file that the player couldn't play. It shows black screen but no any pictures. I am very confused.
  Here is the metadata of the .mp4 file. </p>
  
  <pre><code>General
  Complete name                    : E:\test.mp4
  Format                           : MPEG-4
  Format profile                   : Base Media
  Codec ID                         : isom
  File size                        : 28.2 MiB
  Duration                         : 1mn 30s
  Overall bit rate                 : 2 613 Kbps
  Encoded date                     : UTC 2015-01-09 13:55:04
  Tagged date                      : UTC 2015-01-09 13:55:04
  
  Video
  ID                               : 1
  Format                           : AVC
  Format/Info                      : Advanced Video Codec
  Format profile                   : High@L4.1
  Format settings, CABAC           : Yes
  Format settings, ReFrames        : 1 frame
  Muxing mode                      : Container profile=High@1.3
  Codec ID                         : avc1
  Codec ID/Info                    : Advanced Video Coding
  Duration                         : 1mn 27s
  Bit rate mode                    : Variable
  Bit rate                         : 2 675 Kbps
  Width                            : 756 pixels
  Height                           : 1 260 pixels
  Display aspect ratio             : 0.600
  Frame rate mode                  : Variable
  Frame rate                       : 54.536 fps
  Minimum frame rate               : 4.646 fps
  Maximum frame rate               : 148.515 fps
  Color space                      : YUV
  Chroma subsampling               : 4:2:0
  Bit depth                        : 8 bits
  Scan type                        : Progressive
  Bits/(Pixel*Frame)               : 0.051
  Stream size                      : 27.9 MiB (99%)
  Title                            : VideoHandle
  Language                         : English
  Encoded date                     : UTC 2015-01-09 13:55:04
  Tagged date                      : UTC 2015-01-09 13:55:04
  
  Audio
  ID                               : 2
  Format                           : AMR
  Format/Info                      : Adaptive Multi-Rate
  Format profile                   : Narrow band
  Codec ID                         : samr
  Duration                         : 1mn 30s
  Bit rate mode                    : Constant
  Bit rate                         : 12.8 Kbps
  Channel(s)                       : 1 channel
  Sampling rate                    : 8 000 Hz
  Bit depth                        : 13 bits
  Stream size                      : 141 KiB (0%)
  Title                            : SoundHandle
  Writing library                  :    
  Language                         : English
  Encoded date                     : UTC 2015-01-09 13:55:04
  Tagged date                      : UTC 2015-01-09 13:55:04
  </code></pre>