h.264视频不会在iOS上播放 [英] h.264 video won't play on iOS
问题描述
我有一个用h.264编码的视频文件，不能在iOS上播放，我想知道为什么。以下是HTML：
I have a video file encoded with h.264 that will not play on iOS, and I'd like to know why. Here's the HTML:
<video style="width: 480px; height: 360px;" autoplay controls>
<source src="sample.mp4">
</video>
此视频在桌面浏览器中播放正常，但在iOS设备上，我看到无法点击的播放图标通过它斜杠。我已经看到这意味着视频的编码有问题，但我不知道是什么问题。
This video plays fine in a desktop browser, but on iOS devices I see an un-clickable Play icon with a slash through it. I've read that this means there's a problem with the video's encoding, but I'm not sure what the problem is.
我通过MediaInfo运行视频：
I ran the video through MediaInfo:
General
Format : MPEG-4
Format profile : Base Media
Codec ID : isom
File size : 706 KiB
Duration : 15s 256ms
Overall bit rate mode : Variable
Overall bit rate : 379 Kbps
Video
ID : 1
Format : AVC
Format/Info : Advanced Video Codec
Format profile : Main@L5.1
Format settings, CABAC : Yes
Format settings, ReFrames : 6 frames
Codec ID : avc1
Codec ID/Info : Advanced Video Coding
Duration : 15s 250ms
Bit rate : 311 Kbps
Width : 480 pixels
Height : 360 pixels
Display aspect ratio : 4:3
Frame rate mode : Constant
Frame rate : 24.000 fps
Color space : YUV
Chroma subsampling : 4:2:0
Bit depth : 8 bits
Scan type : Progressive
Bits/(Pixel*Frame) : 0.075
Stream size : 578 KiB (82%)
Audio
ID : 2
Format : AAC
Format/Info : Advanced Audio Codec
Format profile : LC
Codec ID : 40
Duration : 15s 256ms
Bit rate mode : Variable
Bit rate : 62.8 Kbps
Channel(s) : 2 channels
Channel positions : Front: L R
Sampling rate : 44.1 KHz
Compression mode : Lossy
Stream size : 117 KiB (17%)
此外，我通过GSpot运行它，并获得了一些额外的信息：
Also, I ran it through GSpot and got some additional info:
Container
isom: MP4 Base Media v1 [IS0 14496-12:2003]
- mp41: MP4 v1 [ISO 14496-1:ch13]
任何人都可以告诉我为什么此视频不会玩？我知道我可以简单地重新编码视频，如果我这样做，它可以在iOS上播放。但是我想知道原始文件的问题是什么。
Can anyone tell me why this video won't play? I know I can simply re-encode the video, and if I do, it plays fine on iOS. But I'd like to know what the problem with the original file is.
为了比较，这里是MediaInfo分析我重新编码的版本（这个工作原理）：
For comparison, here's the MediaInfo analysis of a re-encoded version I made (this one works):
General
Format : MPEG-4
Format profile : Base Media
Codec ID : isom
File size : 990 KiB
Duration : 15s 256ms
Overall bit rate mode : Variable
Overall bit rate : 532 Kbps
Writing application : Lavf53.19.0
Video
ID : 1
Format : AVC
Format/Info : Advanced Video Codec
Format profile : High@L2.1
Format settings, CABAC : Yes
Format settings, ReFrames : 4 frames
Codec ID : avc1
Codec ID/Info : Advanced Video Coding
Duration : 15s 250ms
Bit rate : 414 Kbps
Width : 480 pixels
Height : 360 pixels
Display aspect ratio : 4:3
Frame rate mode : Constant
Frame rate : 24.000 fps
Color space : YUV
Chroma subsampling : 4:2:0
Bit depth : 8 bits
Scan type : Progressive
Bits/(Pixel*Frame) : 0.100
Stream size : 771 KiB (78%)
Writing library : x264 core 118 r2085 8a62835
Encoding settings : cabac=1 / ref=3 / deblock=1:0:0 / analyse=0x3:0x111 / me=hex / subme=6 / psy=1 / psy_rd=1.00:0.00 / mixed_ref=1 / me_range=16 / chroma_me=1 / trellis=1 / 8x8dct=1 / cqm=0 / deadzone=21,11 / fast_pskip=1 / chroma_qp_offset=-2 / threads=12 / sliced_threads=0 / nr=0 / decimate=1 / interlaced=0 / bluray_compat=0 / constrained_intra=0 / bframes=3 / b_pyramid=2 / b_adapt=1 / b_bias=0 / direct=1 / weightb=1 / open_gop=0 / weightp=2 / keyint=250 / keyint_min=24 / scenecut=40 / intra_refresh=0 / rc_lookahead=40 / rc=crf / mbtree=1 / crf=22.0 / qcomp=0.60 / qpmin=0 / qpmax=69 / qpstep=4 / ip_ratio=1.40 / aq=1:1.00
Audio
ID : 2
Format : AAC
Format/Info : Advanced Audio Codec
Format profile : LC
Codec ID : 40
Duration : 15s 256ms
Bit rate mode : Variable
Bit rate : 111 Kbps
Maximum bit rate : 128 Kbps
Channel(s) : 2 channels
Channel positions : Front: L R
Sampling rate : 44.1 KHz
Compression mode : Lossy
Stream size : 207 KiB (21%)
GSpot关于这个容器的信息是不同的（这可能是为什么这个工作？）：
GSpot's info about this one's container is different (could that be why this one works?):
Container
isom: MP4 Base Media v1 [IS0 14496-12:2003]
- iso2: MP4 Base Media v2 [ISO 14496-12:2005]
- avc1: MP4 Base w/ AVC ext [ISO 14496-12:2005]
- mp41: MP4 v1 [ISO 14496-1:ch13]
只有其他的事情我可以想到的是参考框架的数量（我读过max是3），但是重新编码的版本有4，所以我认为这可能不是。
The only other thing I can think of is the number of reference frames (I've read the max is 3), but the re-encoded version has 4 so I figure that's probably not it.
推荐答案
找到解决方案到我自己的问题：
Found the solution to my own question:
问题是， h.264主配置文件级别5.1，而iOS仅支持AVC级别3.1（更多信息 here ）。
The problem was that the video used the h.264 Main Profile level 5.1, while iOS only supports AVC level 3.1 (more info here).
我通过以下这些说明使用十六进制编辑器更改配置文件和级别字节。在ASCII中或 61 76 63 43 中以十六进制形式搜索文件 avcC 。第一个字节通常是 01 ，对此不重要，但之后应该是以下之一：
I confirmed this by following these instructions to change the profile and level bytes using a hex editor. Search the file for avcC in ASCII or 61 76 63 43 in hex. The first byte is usually 01 and is unimportant to this purpose, but after that should be one of the following:
42 E0 – for Baseline Profile
4D 40 – for Main Profile
58 A0 – for Extended Profile
64 00 – for High Profile
之后的数字是十六进制中的级别（不带小数点），例如：
The number after that is the level (without the decimal point) in hex, e.g.:
1F (31 in dec) is level 3.1
29 (41 in dec) is level 4.1
33 (51 in dec) is level 5.1
如果您查找和替换配置文件/级别字节的所有实例（例如，搜索 4D 40 33 并替换所需的字节 - 在我的情况下， 4D 40 1F ），视频应现在玩iOS。请注意，许多网页帮助页面说iOS需要基准配置文件，但这似乎不是真的。只要AVC级别为3.1，主要作品就可以正常使用。
If you do a find and replace of all instances of the profile/level bytes (e.g., search 4D 40 33 and replace with the bytes you want--in my case 4D 40 1F), the video should now play on iOS. Note that many web help pages say iOS requires the Baseline profile, but that doesn't appear to be true. Main works fine as long as the AVC level is 3.1.
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