最近发现 服务器端 ffmpeg 截图失败，经过分析和测试 超多25M 的视频就截图失败。小视频截图都OK
服务器测试大视频结果如下：
[root@AY130527135215496204Z video]# ffmpeg -i 13801894211317.flv -y -f image2 -ss 8 -t 0.001 -s 350x240 test.jpg
ffmpeg version 0.10.1 Copyright (c) 2000-2012 the FFmpeg developers
built on Sep 24 2013 14:00:05 with gcc 4.1.2 20080704 (Red Hat 4.1.2-54)
configuration: --enable-shared --prefix=/usr/local/ffmpeg
libavutil 51. 35.100 / 51. 35.100
libavcodec 53. 61.100 / 53. 61.100
libavformat 53. 32.100 / 53. 32.100
libavdevice 53. 4.100 / 53. 4.100
libavfilter 2. 61.100 / 2. 61.100
libswscale 2. 1.100 / 2. 1.100
libswresample 0. 6.100 / 0. 6.100
Input #0, flv, from '13801894211317.flv':
Metadata:
metadatacreator : iku
hasKeyframes : true
hasVideo : true
hasAudio : true
hasMetadata : true
canSeekToEnd : false
datasize : 28912577
videosize : 25317440
audiosize : 3477217
lasttimestamp : 809
lastkeyframetimestamp: 798
lastkeyframelocation: 28846240
Duration: 00:13:29.16, start: 0.000000, bitrate: 285 kb/s
Stream #0:0: Video: h264 (High), yuv420p, 592x256 [SAR 1:1 DAR 37:16], 248 kb/s, 15 tbr, 1k tbn, 30 tbc
Stream #0:1: Audio: aac, 44100 Hz, stereo, s16, 32 kb/s
Incompatible pixel format 'yuv420p' for codec 'mjpeg', auto-selecting format 'yuvj420p'
[buffer @ 0x91dbf80] w:592 h:256 pixfmt:yuv420p tb:1/1000000 sar:1/1 sws_param:
[scale @ 0x91d10c0] w:592 h:256 fmt:yuv420p -> w:350 h:240 fmt:yuvj420p flags:0x4
Output #0, image2, to 'test.jpg':
Metadata:
metadatacreator : iku
hasKeyframes : true
hasVideo : true
hasAudio : true
hasMetadata : true
canSeekToEnd : false
datasize : 28912577
videosize : 25317440
audiosize : 3477217
lasttimestamp : 809
lastkeyframetimestamp: 798
lastkeyframelocation: 28846240
encoder : Lavf53.32.100
Stream #0:0: Video: mjpeg, yuvj420p, 350x240 [SAR 111:70 DAR 37:16], q=2-31, 200 kb/s, 90k tbn, 15 tbc
Stream mapping:
Stream #0:0 -> #0:0 (h264 -> mjpeg)
Press [q] to stop, [?] for help
frame= 0 fps= 0 q=0.0 Lsize= 0kB time=00:00:00.00 bitrate= 0.0kbits/s
video:0kB audio:0kB global headers:0kB muxing overhead nan%
Output file is empty, nothing was encoded (check -ss / -t / -frames parameters if used)