流化mp4文件被darwin流媒体服务器支持

正常的MP4文件应该是没有被流化，如果要被darwin stream server支持，必须hint该MP4文件。

  关于hint的解释，如下面一段英文：

  Hint tracks are a series of instructions in a mp4 container file that
tell a server how to transmit packets. Hint tracks always refer
to another track, most likely an audio or video media track.    
   This series of instructions tells the server when to send the packet,  
what type of RTP header to add, if there is any extra data in the
packet, and how much data to send in the packet. To save on space,  
a hint can contain a pointer to the media track, instead of duplicating
that data.
   It will also tell what SDP to add for the track that is referenced. 
   So a file that is hinted should have a media track, and an associated
hint track for that media track. There are some mp4 container files
that just have hint tracks - these are called "fat hints" and are
usually not playable locally. These are illegal in ISMA, so we won 't
talk about them.
   To create hint tracks for a mp4 file is fairly simple with the mp4creator
program. Just execute the:
    mp4creator   -hint= <track   to   hint   track   number>   <mp4file>

例如：

1）被hint之前mp4文件的信息，用mp4info查看文件信息如下：

mp4info  ./1.mp4
mp4info version 1.6
./1.mp4:
Track   Type    Info
1       audio   MPEG-4 AAC LC, 662.165 secs, 121 kbps, 48000 Hz
2       video   H264 Main@5.1, 662.562 secs, 1756 kbps, 640x368 @ 29.970025 fps

2）hint 音频

mp4creator -hint=1  ./1.mp4

3）hint视频

 mp4creator -hint=2 ./2.mp4

4）查看hint之后的mp4文件信息

mp4info  ./1.mp4
mp4info version 1.6
./1.mp4:
Track   Type    Info
1       audio   MPEG-4 AAC LC, 662.165 secs, 121 kbps, 48000 Hz
2       video   H264 Main@5.1, 662.562 secs, 1756 kbps, 640x368 @ 29.970025 fps
3       hint    Payload mpeg4-generic for track 1
4       hint    Payload H264 for track 2
 Tool: mp4creator 1.5.0.1

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