使用ffmpeg for Android对x264视频进行编码（起始偏移量）

Question

I'm trying to convert a video to play on an Android device. The video is from a big movie. I am chopping it back into pieces to correspond with the actual segments of the movie using -ss and -t.

The input is mp4 with H.264 and AAC. The output is mkv using H.264 and Vorbis.

Specifically, the input is:

Stream #0:0(und): Video: h264 (Main) (avc1 / 0x31637661), yuv420p, 320x240, 2240 kb/s, 29.97 fps, 60 tbr, 90k tbn, 180k tbc
Stream #0:1(und): Audio: aac (mp4a / 0x6134706D), 48000 Hz, stereo, s16, 162 kb/s

I'm using: ffmpeg version 1.0.7

The command I'm trying is something like:

ffmpeg -ss 00:03:52.000 -i in.mp4 -t 00:01:00.000 -c:v libx264 -preset medium -crf 20 -maxrate 400k -bufsize 1835k -c:a libvorbis -sn out.mkv

However, while the resulting video works fine on my computer, when I click on my phone, it says: Can't play video and checking the Android log, it has:

E/SoftAVC (24319): Decoder failed: -2
E/OMXCodec(24319): [OMX.google.h264.decoder] ERROR(0x80001001, -1007)

It is still able to make a thumbnail for the movie, but not play it.

Interestingly, some simple variations of that command do work: Remove -ss to start at the beginning of the video Use -an to disable audio

These variations still failed: Copying the original audio with -c:a copy, or other audio codecs like vorbis, mp3 Using mp4 instead of mkv Using baseline H.264 profile, including restricting level to 1.2.

Running through mkvmerge first not only fails, but makes Android not able to even make a thumbnail.

I don't know if it is related, but another small thing I noticed is that for starting transcoding later in the movie, the audio starts out slightly out-of-sync. After several seconds, it gets back in sync. The audio is in sync in the original.

Robert Rowntree:

-vcodec libx264 -b:v 200k -bt 50k -threads 0 -b_strategy 1 -acodec copy -f mp4 -strict -2

Interesting. Your command almost works. The video actually plays on Android. The one problem is that the audio is out-of-sync and stays out-of-sync throughout the whole clip. But, that's much closer than I've been. I'll search around there and see if I can find the right combination.

I tried combinations of it. It appears that using both mp4 and copying the audio is what allows it to work. Using libvorbis or going to mkv breaks it again. But, I would like to transcode the audio, and I suspect to keep it in sync, I might have to transcode it anyways. Note that even with transcoding, when I play it back on the computer, I still don't have sync between audio and video.

LordNeckbeard: Here is the complete log.

ffmpeg version 1.0.7 Copyright (c) 2000-2013 the FFmpeg developers
  built on Jul 27 2013 13:01:19 with gcc 4.4.5 (Gentoo 4.4.5 p1.2, pie-0.4.5)
  configuration: --prefix=/usr --libdir=/usr/lib64 --shlibdir=/usr/lib64 --mandir=/usr/share/man --enable-shared --cc=x86_64-pc-linux-gnu-gcc --cxx=x86_64-pc-linux-gnu-g++ --ar=x86_64-pc-linux-gnu-ar --optflags='-mtune=athlon64 -O2 -pipe -fomit-frame-pointer -fstack-protector' --extra-cflags='-mtune=athlon64 -O2 -pipe -fomit-frame-pointer -fstack-protector' --extra-cxxflags='-mtune=athlon64 -O2 -pipe -fomit-frame-pointer -fstack-protector' --disable-static --enable-gpl --enable-version3 --enable-postproc --enable-avfilter --enable-avresample --disable-stripping --disable-debug --disable-doc --disable-vaapi --disable-runtime-cpudetect --enable-libmp3lame --enable-libvo-aacenc --enable-libtheora --enable-libx264 --enable-libxvid --enable-libcaca --enable-openal --disable-indev=v4l2 --disable-indev=oss --disable-indev=jack --enable-x11grab --disable-outdev=oss --enable-libfreetype --enable-pthreads --enable-libspeex --enable-libvorbis --disable-altivec --disable-avx --disable-vis --disable-neon --cpu=athlon64 -  libavutil      51. 73.101 / 51. 73.101
  libavcodec     54. 59.100 / 54. 59.100
  libavformat    54. 29.104 / 54. 29.104
  libavdevice    54.  2.101 / 54.  2.101
  libavfilter     3. 17.100 /  3. 17.100
  libswscale      2.  1.101 /  2.  1.101
  libswresample   0. 15.100 /  0. 15.100
  libpostproc    52.  0.100 / 52.  0.100
Input #0, mov,mp4,m4a,3gp,3g2,mj2, from 'in.mp4':
  Metadata:
    major_brand     : mp42
    minor_version   : 0
    compatible_brands: mp42isomavc1
    creation_time   : 2013-07-13 02:23:51
    encoder         : HandBrake 0.9.6 2012022800
  Duration: 03:14:01.41, start: 0.000000, bitrate: 2408 kb/s
    Chapter #0.0: start -0.133467, end 648.697411
    Metadata:
      title           : Chapter  1
    Chapter #0.1: start 648.697411, end 1297.345411
    Metadata:
      title           : Chapter  2
    Chapter #0.2: start 1297.345411, end 1729.777411
    Metadata:
      title           : Chapter  3
    Chapter #0.3: start 1729.777411, end 2378.425411
    Metadata:
      title           : Chapter  4
    Chapter #0.4: start 2378.425411, end 3027.073411
    Metadata:
      title           : Chapter  5
    Chapter #0.5: start 3027.073411, end 3675.721411
    Metadata:
      title           : Chapter  6
    Chapter #0.6: start 3675.721411, end 4108.153411
    Metadata:
      title           : Chapter  7
    Chapter #0.7: start 4108.153411, end 4756.801411
    Metadata:
      title           : Chapter  8
    Chapter #0.8: start 4756.801411, end 5405.449411
    Metadata:
      title           : Chapter  9
    Chapter #0.9: start 5405.449411, end 6054.097411
    Metadata:
      title           : Chapter 10
    Chapter #0.10: start 6054.097411, end 6702.745411
    Metadata:
      title           : Chapter 11
    Chapter #0.11: start 6702.745411, end 7135.177411
    Metadata:
      title           : Chapter 12
    Chapter #0.12: start 7135.177411, end 7783.825411
    Metadata:
      title           : Chapter 13
    Chapter #0.13: start 7783.825411, end 8432.473411
    Metadata:
      title           : Chapter 14
    Chapter #0.14: start 8432.473411, end 9081.121411
    Metadata:
      title           : Chapter 15
    Chapter #0.15: start 9081.121411, end 9513.553411
    Metadata:
      title           : Chapter 16
    Chapter #0.16: start 9513.553411, end 10162.201411
    Metadata:
      title           : Chapter 17
    Chapter #0.17: start 10162.201411, end 10810.849411
    Metadata:
      title           : Chapter 18
    Chapter #0.18: start 10810.849411, end 11459.497411
    Metadata:
      title           : Chapter 19
    Chapter #0.19: start 11459.497411, end 11641.412478
    Metadata:
      title           : Chapter 20
    Stream #0:0(und): Video: h264 (Main) (avc1 / 0x31637661), yuv420p, 320x240, 2240 kb/s, 29.97 fps, 60 tbr, 90k tbn, 180k tbc
    Metadata:
      creation_time   : 2013-07-13 02:23:51
    Stream #0:1(und): Audio: aac (mp4a / 0x6134706D), 48000 Hz, stereo, s16, 162 kb/s
    Metadata:
      creation_time   : 2013-07-13 02:23:51
    Stream #0:2(und): Subtitle: mov_text (text / 0x74786574)
    Metadata:
      creation_time   : 2013-07-13 02:23:51
[libx264 @ 0x14ea220] using cpu capabilities: MMX2 SSE2Slow SlowCTZ
[libx264 @ 0x14ea220] profile High, level 2.1
[libx264 @ 0x14ea220] 264 - core 120 - H.264/MPEG-4 AVC codec - Copyleft 2003-2011 - http://www.videolan.org/x264.html - options: cabac=1 ref=3 deblock=1:0:0 analyse=0x3:0x113 me=hex subme=7 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=3 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=60 keyint_min=6 scenecut=40 intra_refresh=0 rc_lookahead=40 rc=crf mbtree=1 crf=20.0 qcomp=0.60 qpmin=0 qpmax=69 qpstep=4 vbv_maxrate=400 vbv_bufsize=1835 crf_max=0.0 nal_hrd=none ip_ratio=1.40 aq=1:1.00
Output #0, matroska, to 'out.mkv':
  Metadata:
    major_brand     : mp42
    minor_version   : 0
    compatible_brands: mp42isomavc1
    encoder         : Lavf54.29.104
    Chapter #0.0: start 0.000000, end 60.000000
    Metadata:
      title           : Chapter  1
    Stream #0:0(und): Video: h264 (H264 / 0x34363248), yuv420p, 320x240, q=-1--1, 1k tbn, 60 tbc
    Metadata:
      creation_time   : 2013-07-13 02:23:51
    Stream #0:1(und): Audio: vorbis (oV[0][0] / 0x566F), 48000 Hz, stereo, flt
    Metadata:
      creation_time   : 2013-07-13 02:23:51
Stream mapping:
  Stream #0:0 -> #0:0 (h264 -> libx264)
  Stream #0:1 -> #0:1 (aac -> libvorbis)
Press [q] to stop, [?] for help
frame= 1799 fps= 92 q=-1.0 Lsize=    3738kB time=00:00:59.98 bitrate= 510.5kbits/s dup=0 drop=51    =51    
video:3016kB audio:683kB subtitle:0 global headers:4kB muxing overhead 0.939943%
[libx264 @ 0x14ea220] frame I:31    Avg QP:20.23  size: 14126
[libx264 @ 0x14ea220] frame P:634   Avg QP:23.03  size:  3317
[libx264 @ 0x14ea220] frame B:1134  Avg QP:27.71  size:   482
[libx264 @ 0x14ea220] consecutive B-frames:  2.3% 12.8% 84.7%  0.2%
[libx264 @ 0x14ea220] mb I  I16..4:  3.8% 63.8% 32.4%
[libx264 @ 0x14ea220] mb P  I16..4:  0.1%  0.3%  0.1%  P16..4: 47.4% 30.2% 19.5%  0.0%  0.0%    skip: 2.4%
[libx264 @ 0x14ea220] mb B  I16..4:  0.0%  0.0%  0.0%  B16..8: 35.2%  3.0%  0.6%  direct: 8.8%  skip:52.3%  L0:28.7% L1:63.9% BI: 7.4%
[libx264 @ 0x14ea220] 8x8 transform intra:64.0% inter:59.5%
[libx264 @ 0x14ea220] coded y,uvDC,uvAC intra: 94.2% 99.5% 95.5% inter: 23.3% 55.5% 14.0%
[libx264 @ 0x14ea220] i16 v,h,dc,p: 75% 10%  5% 10%
[libx264 @ 0x14ea220] i8 v,h,dc,ddl,ddr,vr,hd,vl,hu: 19% 16% 12%  8%  7%  8%  8% 11% 11%
[libx264 @ 0x14ea220] i4 v,h,dc,ddl,ddr,vr,hd,vl,hu: 17% 20%  7%  8%  9%  9% 10% 10% 11%
[libx264 @ 0x14ea220] i8c dc,h,v,p: 38% 31% 14% 17%
[libx264 @ 0x14ea220] Weighted P-Frames: Y:7.3% UV:4.4%
[libx264 @ 0x14ea220] ref P L0: 48.8% 14.2% 29.1%  7.5%  0.4%
[libx264 @ 0x14ea220] ref B L0: 65.4% 30.8%  3.7%
[libx264 @ 0x14ea220] ref B L1: 89.0% 11.0%
[libx264 @ 0x14ea220] kb/s:411.70

Answer 1

Upgrading to ffmpeg 1.2.1 fixed the compatibility issue. After that, my Android phone was able to play the videos just fine.

The -ss option is trickier than it at first looks. It has a different meaning based on whether it is before or after -i. It turns out, to make it work, you have to use both. You put the main offset before -i, which makes ffmpeg skip to that point in the stream. But, then you also need a small non-zero offset AFTER -i to make it seek to that point within the stream so audio and video will be in sync.

For reference, the final working command is:

ffmpeg -ss 00:03:52.00 -i in.mp4 -ss 0.1 -t 01:28:33.00 -c:v libx264 -preset medium -crf 20 -maxrate 400k -bufsize 1835k -c:a libvorbis -sn out.mkv