如何在线查看mp4视频的编码格式，是否为iOS兼容的h264格式

记录一下，可以在线查询mp4编码格式的网站：

https://gpac.github.io/mp4box.js/test/filereader.html

通常H264的格式的文件编码信息如下：

Movie Info

File Size / Bitrate： 0 bytes / 0 kbps
Duration / Timescale： 220845/1000 (0:03:40.845)
Brands (major/compatible)： isom,isom,iso2,avc1,mp41
MIME： video/mp4; codecs="avc1.42c01f,mp4a.40.2"; profiles="isom,iso2,avc1,mp41"
Progressive： false
Fragmented： false
MPEG-4 IOD： false

重点查看MIME类型是否为video/mp4，是否包含avc信息。且 Progressive/Fragmented/MPEG-4 IOD 三个参数为false。

另外iOS支持的编码格式可以通过官方查看：
https://developer.apple.com/library/archive/documentation/NetworkingInternet/Conceptual/StreamingMediaGuide/FrequentlyAskedQuestions/FrequentlyAskedQuestions.html

What are the specifics of the video and audio formats supported?
Although the protocol specification does not limit the video and audio formats, the current Apple implementation supports the following formats:

• Video:
  H.264 Baseline Level 3.0, Baseline Level 3.1, Main Level 3.1, and High Profile Level 4.1.

• Audio:
  HE-AAC or AAC-LC up to 48 kHz, stereo audio
  MP3 (MPEG-1 Audio Layer 3) 8 kHz to 48 kHz, stereo audio
  AC-3 (for Apple TV, in pass-through mode only)