我使用DASH实现了一个带有视频播放器的概念验证页面。我很难获得正确的视频，我不确定这是编码问题还是MP4Box问题。
由于我正在使用Ubuntu，我不得不为ffmpeg更改一些参数，但根据我的阅读，这应该没问题：
~/ffmpeg/ffmpeg -c:a aac -ar 44100 -ac 1 -codec:v libx264 \
-profile:v baseline -level 13 -b:v 2000k video_transcoded.mp4 -i video.mp4
然后创建MPD我正在运行：
MP4Box -dash 10000 -dash-profile live \
-segment-name video_transcoded video_transcoded.mp4
我最后得到了这个回复，这可能就是为什么没有玩家会播放我的视频的原因：
[DASH] two languages in adaptation set: und will be kept eng will be ignored
DASHing file video_transcoded.mp4
[DASH]: Segment duration variation is higher than the +/- 50% allowed by DASH-IF (min 1.044, max 10.448) - please reconsider encoding
这是ffmpeg的输出：
ffmpeg version N-53477-g689211d-static http://johnvansickle.com/ffmpeg/ Copyright (c) 2000-2016 the FFmpeg developers
built with gcc 5.3.1 (Debian 5.3.1-10) 20160224
configuration: --enable-gpl --enable-version3 --disable-shared --disable-debug --enable-runtime-cpudetect --enable-libmp3lame --enable-libx264 --enable-libx265 --enable-libwebp --enable-libspeex --enable-libvorbis --enable-libvpx --enable-libfreetype --enable-fontconfig --enable-libxvid --enable-libopencore-amrnb --enable-libopencore-amrwb --enable-libtheora --enable-libvo-amrwbenc --enable-gray --enable-libopenjpeg --enable-libopus --enable-libass --enable-gnutls --enable-libvidstab --enable-libsoxr --enable-frei0r --enable-libfribidi --disable-indev=sndio --disable-outdev=sndio --enable-librtmp --enable-libmfx --cc=gcc
libavutil 55. 19.100 / 55. 19.100
libavcodec 57. 28.100 / 57. 28.100
libavformat 57. 28.100 / 57. 28.100
libavdevice 57. 0.101 / 57. 0.101
libavfilter 6. 39.102 / 6. 39.102
libswscale 4. 0.100 / 4. 0.100
libswresample 2. 0.101 / 2. 0.101
libpostproc 54. 0.100 / 54. 0.100
Input #0, mov,mp4,m4a,3gp,3g2,mj2, from 'gladiator.mp4':
Metadata:
major_brand : isom
minor_version : 1
compatible_brands: isomavc1
creation_time : 2013-02-12 19:14:56
Duration: 02:50:56.98, start: 0.000000, bitrate: 923 kb/s
Stream #0:0(und): Video: h264 (High) (avc1 / 0x31637661), yuv420p, 1280x544 [SAR 1:1 DAR 40:17], 823 kb/s, 23.98 fps, 23.98 tbr, 24k tbn, 47.95 tbc (default)
Metadata:
creation_time : 2013-02-12 19:14:56
handler_name : 2000.Extended.Remastered.720p.BluRay.x264-HDEVO.mkv.264#trackID=1:fps=23.976@GPAC0.5.1-DEV-rev4283
Stream #0:1(eng): Audio: aac (LC) (mp4a / 0x6134706D), 48000 Hz, stereo, fltp, 95 kb/s (default)
Metadata:
creation_time : 2013-02-12 15:32:26
handler_name : Sound Media Handler
[libx264 @ 0xaf12920] using SAR=1/1
[libx264 @ 0xaf12920] frame MB size (80x34) > level limit (396)
[libx264 @ 0xaf12920] DPB size (3 frames, 8160 mbs) > level limit (0 frames, 2376 mbs)
[libx264 @ 0xaf12920] MB rate (65214) > level limit (11880)
[libx264 @ 0xaf12920] using cpu capabilities: MMX2 SSE2Fast SSSE3 SSE4.2 AVX
[libx264 @ 0xaf12920] profile Constrained Baseline, level 1.3
[libx264 @ 0xaf12920] 264 - core 148 r236 a01e339 - H.264/MPEG-4 AVC codec - Copyleft 2003-2016 - http://www.videolan.org/x264.html - options: cabac=0 ref=3 deblock=1:0:0 analyse=0x1:0x111 me=hex subme=7 psy=1 psy_rd=1.00:0.00 mixed_ref=1 me_range=16 chroma_me=1 trellis=1 8x8dct=0 cqm=0 deadzone=21,11 fast_pskip=1 chroma_qp_offset=-2 threads=1 lookahead_threads=1 sliced_threads=0 nr=0 decimate=1 interlaced=0 bluray_compat=0 constrained_intra=0 bframes=0 weightp=0 keyint=250 keyint_min=23 scenecut=40 intra_refresh=0 rc_lookahead=40 rc=abr mbtree=1 bitrate=2000 ratetol=1.0 qcomp=0.60 qpmin=0 qpmax=69 qpstep=4 ip_ratio=1.40 aq=1:1.00
Output #0, mp4, to 'gladiator2.mp4':
Metadata:
major_brand : isom
minor_version : 1
compatible_brands: isomavc1
encoder : Lavf57.28.100
Stream #0:0(und): Video: h264 (libx264) ([33][0][0][0] / 0x0021), yuv420p, 1280x544 [SAR 1:1 DAR 40:17], q=-1--1, 2000 kb/s, 23.98 fps, 24k tbn, 23.98 tbc (default)
Metadata:
creation_time : 2013-02-12 19:14:56
handler_name : 2000.Extended.Remastered.720p.BluRay.x264-HDEVO.mkv.264#trackID=1:fps=23.976@GPAC0.5.1-DEV-rev4283
encoder : Lavc57.28.100 libx264
Side data:
cpb: bitrate max/min/avg: 0/0/2000000 buffer size: 0 vbv_delay: -1
Stream #0:1(eng): Audio: aac (LC) ([64][0][0][0] / 0x0040), 44100 Hz, mono, fltp, 69 kb/s (default)
Metadata:
creation_time : 2013-02-12 15:32:26
handler_name : Sound Media Handler
encoder : Lavc57.28.100 aac
Stream mapping:
Stream #0:0 -> #0:0 (h264 (native) -> h264 (libx264))
Stream #0:1 -> #0:1 (aac (native) -> aac (native))
Press [q] to stop, [?] for help
转码完成后，我明白了：
frame= 132 fps= 15 q=25.0 Lsize= 1112kB time=00:00:05.31 bitrate=1713.0kbits/s speed=0.603x
video:1062kB audio:45kB subtitle:0kB other streams:0kB global headers:0kB muxing overhead: 0.414602%
[libx264 @ 0xab63de0] frame I:1 Avg QP:21.29 size:121187
[libx264 @ 0xab63de0] frame P:131 Avg QP:23.40 size: 7372
[libx264 @ 0xab63de0] mb I I16..4: 9.2% 0.0% 90.8%
[libx264 @ 0xab63de0] mb P I16..4: 0.9% 0.0% 0.3% P16..4: 37.2% 7.0% 1.8% 0.0% 0.0% skip:52.7%
[libx264 @ 0xab63de0] final ratefactor: 21.58
[libx264 @ 0xab63de0] coded y,uvDC,uvAC intra: 48.8% 72.2% 30.7% inter: 8.9% 14.6% 0.8%
[libx264 @ 0xab63de0] i16 v,h,dc,p: 28% 33% 18% 21%
[libx264 @ 0xab63de0] i4 v,h,dc,ddl,ddr,vr,hd,vl,hu: 22% 16% 15% 8% 7% 8% 6% 12% 6%
[libx264 @ 0xab63de0] i8c dc,h,v,p: 52% 21% 19% 8%
[libx264 @ 0xab63de0] ref P L0: 92.9% 5.2% 1.8%
[libx264 @ 0xab63de0] kb/s:1646.80
[aac @ 0xab64c40] Qavg: 112.650
我可以做些什么来完成这项工作？
答案 0 :(得分：0)
您需要在ffmpeg命令中设置gop大小：
-g NUMBER_OF_FRAMES
示例ffmpeg命令可能如下所示：
ffmpeg -i input_video.mp4 -c：libfaac -ar 48000 -b：128k -c：v libx264 -preset slow -sc_threshold 0 -r 24 -g 96 -s 1280x720 -b：v 2000k output.mp4
此博客文章中还介绍了编码，打包和播放的完整工作流程：mpeg-dash content generation using x264 and mp4box
另一种选择是您使用服务对您的测试内容进行编码，例如bitmovin encoding service（具有2.5GB的免费计划）。