我从YouTube上下了一个1280x720的mp4格式视频，结果手机放不了，用格式工厂再次转换1280x720的mp4就可以放了，这是怎么回事？我的手机是MOTO XT788

General
Complete name : D:\My Documents\下载\M4SONIC - Weapon (Live Launchpad Mashup).mp4
Format : MPEG-4
Format profile : Base Media / Version 2
Codec ID : mp42
File size : 42.7 MiB
Duration : 2mn 52s
Overall bit rate : 2 083 K
bp
s
Encoded date : UTC 2012-07-09 13:17:52
Tagged date : UTC 2012-07-09 13:17:52
gsst : 0
gstd : 172128
gssd : B4A7DD628HH
13602431178
94813
gshh : r8---sn-p5qlsu7l.c.youtube.com
Video
ID : 1
Format : AVC
Format/Info : Advanced Video Codec
Format profile : [email protected]
Format settings, CABAC : Yes
Format settings, ReFrames : 1 frame
Codec ID : avc1
Codec ID/Info : Advanced Video Coding
Duration : 2mn 52s
Bit rate mode : Variable
Bit rate : 1 928 Kbps
Maximum bit rate : 2 308 Kbps
Width : 1 280 pixels
Height : 720 pixels
Display aspect ratio : 16:9
Frame rate mode : Constant
Frame rate : 29.970 fps
Color space : YUV
Chroma subsampling : 4:2:0
Bit depth : 8 bits
Scan type : Progressive
Bits/(Pixel*Frame) : 0.070
Stream size : 39.5 MiB (93%)
Tagged date : UTC 2012-07-09 13:17:53
Audio
ID : 2
Format : AAC
Format/Info : Advanced Audio Codec
Format profile : LC
Codec ID : 40
Duration : 2mn 52s
Bit rate mode : Variable
Bit rate : 152 Kbps
Maximum bit rate : 228 Kbps
Channel(s) : 2 channels
Channel positions : Front: L R
Sampling rate : 44.1 KHz
Compression mode : Lossy
Stream size : 3.12 MiB (7%)
Title : IsoMedia File Produced by Google, 5-11-2011
Encoded date : UTC 2012-07-09 13:17:53
Tagged date : UTC 2012-07-09 13:17:53
这个是从YouTube上下的

General
Complete name : D:\My Documents\FFOutput\M4SONIC - Weapon (Live Launchpad Mashup)(1).mp4
Format : MPEG-4
Format profile : Base Media / Version 2
Codec ID : mp42
File size : 73.6 MiB
Duration : 2mn 51s
Overall bit rate : 3 590 Kbps
Encoded date : UTC 2013-02-07 13:23:20
Tagged date : UTC 2013-02-07 13:23:28
Writing application : mp4creator 1.6.1d
Video
ID : 1
Format : MPEG-4 Visual
Format profile : Simple@L1
Format settings, BVOP : No
Format settings, QPel : No
Format settings, GMC : No warppoints
Format settings, Matrix : Default (H.263)
Codec ID : 20
Duration : 2mn 51s
Bit rate mode : Variable
Bit rate : 3 449 Kbps
Maximum bit rate : 5 299 Kbps
Width : 1 280 pixels
Height : 720 pixels
Display aspect ratio : 16:9
Frame rate mode : Variable
Frame rate : 29.970 fps
Minimum frame rate : 29.960 fps
Maximum frame rate : 29.970 fps
Color space : YUV
Chroma subsampling : 4:2:0
Bit depth : 8 bits
Scan type : Progressive
Compression mode : Lossy
Bits/(Pixel*Frame) : 0.125
Stream size : 70.7 MiB (96%)
Language : English
Encoded date : UTC 2013-02-07 13:23:20
Tagged date : UTC 2013-02-07 13:23:28
Audio
ID : 2
Format : AAC
Format/Info : Advanced Audio Codec
Format profile : LC
Codec ID : 40
Duration : 2mn 51s
Bit rate mode : Variable
Bit rate : 139 Kbps
Maximum bit rate : 243 Kbps
Channel(s) : 2 channels
Channel positions : Front: L R
Sampling rate : 44.1 KHz
Compression mode : Lossy
Stream size : 2.84 MiB (4%)
Language : English
Encoded date : UTC 2013-02-07 13:23:28
Tagged date : UTC 2013-02-07 13:23:28
这个是再次转换过的

http://blog.csdn.net/yue_wu151/article/details/6053563

那个帖子是详细描述了MP4文件的字节序，对于你遇到的这个问题是没有必要那么深究了。从你显示出的文件信息来看，视频的编码格式是AVC，也就是H264编码，转码后视频编码成为MPEG-4，这也就说明你的手机内嵌的播放器不支持对AVC的视频编码进行解码。如果想验证这一点，你可以在转码的时候，保证视频格式以外的其它视频参数均相同，如帧率模式（Frame rate mode）。

有可能是视频采用的编码方式是你手机不支持的