webm to mp4 conversion using ffmpeg

问题:

When I try to convert a webm file to mp4 the output is very very choppy and it appears as if many frames have been dropped by ffmpeg

I used the following commands to convert

ffmpeg -i movie.webm movie.mp4
ffmpeg -i movie.webm -vcodec libx264 movie.mp4
ffmpeg -i movie.webm -vcodec libx264 -qscale 0 movie.mp4

All of them have the same problem. When I use ffprobe it seems to show the frames more or less properly.

UPDATE:

 built on Jun 14 2013 14:31:50 with gcc 4.7 (Ubuntu/Linaro 4.7.2-2ubuntu1)
  configuration: --prefix=/home/user2/ffmpeg_build --extra-cflags=-I/home/user2/ffmpeg_build/include --extra-ldflags=-L/home/pavan4/ffmpeg_build/lib --bindir=/home/pavan4/bin --extra-libs=-ldl --enable-gpl --enable-libass --enable-libfdk-aac --enable-libmp3lame --enable-libtheora --enable-libvorbis --enable-libvpx --enable-libx264 --enable-nonfree --enable-x11grab
  libavutil      52. 35.101 / 52. 35.101
  libavcodec     55. 16.100 / 55. 16.100
  libavformat    55.  8.102 / 55.  8.102
  libavdevice    55.  2.100 / 55.  2.100
  libavfilter     3. 77.101 /  3. 77.101
  libswscale      2.  3.100 /  2.  3.100
  libswresample   0. 17.102 /  0. 17.102
  libpostproc    52.  3.100 / 52.  3.100
Hyper fast Audio and Video encoder
usage: ffmpeg [options] [[infile options] -i infile]... {[outfile options] outfile}...

Use -h to get full help or, even better, run 'man ffmpeg'

Input #0, matroska,webm, from '1.webm':
  Duration: 00:00:10.64, start: 0.000000, bitrate: 5024 kb/s
    Stream #0:0(eng): Video: vp8, yuv420p, 1280x720, SAR 1:1 DAR 16:9, 1k fps, 1k tbr, 1k tbn, 1k tbc (default)
[libx264 @ 0x1d966a0] using SAR=1/1
[libx264 @ 0x1d966a0] MB rate (3600000) > level limit (2073600)
[libx264 @ 0x1d966a0] using cpu capabilities: MMX2 SSE2Fast SSSE3 SSE4.2
[libx264 @ 0x1d966a0] profile High, level 5.2
[libx264 @ 0x1d966a0] 264 - core 133 r2 a3ac64b - H.264/MPEG-4 AVC codec - Copyleft 2003-2013 - 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=12 lookahead_threads=2 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=25 scenecut=40 intra_refresh=0 rc_lookahead=40 rc=crf mbtree=1 crf=23.0 qcomp=0.60 qpmin=0 qpmax=69 qpstep=4 ip_ratio=1.40 aq=1:1.00
Output #0, mp4, to '1_conv4.mp4':
  Metadata:
    encoder         : Lavf55.8.102
    Stream #0:0(eng): Video: h264 (libx264) ([33][0][0][0] / 0x0021), yuv420p, 1280x720 [SAR 1:1 DAR 16:9], q=-1--1, 16k tbn, 1k tbc (default)
Stream mapping:
Stream #0:0 -> #0:0 (vp8 -> libx264)
Press [q] to stop, [?] for help
frame=  168 fps=0.0 q=33.0 size=      62kB time=00:00:00.11 bitrate=4606.0kbits/frame=  293 fps=230 q=33.0 size=     138kB time=00:00:00.23 bitrate=4809.7kbits/

video:5620kB audio:0kB subtitle:0 global headers:0kB muxing overhead 2.212461%
[libx264 @ 0x1d966a0] frame I:46    Avg QP:18.50  size: 39849
[libx264 @ 0x1d966a0] frame P:2940  Avg QP:18.27  size:  1222
[libx264 @ 0x1d966a0] frame B:7651  Avg QP:17.68  size:    43
[libx264 @ 0x1d966a0] consecutive B-frames:  4.0%  0.2%  0.3% 95.5%
[libx264 @ 0x1d966a0] mb I  I16..4: 19.9% 63.2% 16.9%
[libx264 @ 0x1d966a0] mb P  I16..4:  0.2%  0.5%  0.1%  P16..4:  3.9%  1.1%  0.6%  0.0%  0.0%    skip:93.6%
[libx264 @ 0x1d966a0] mb B  I16..4:  0.0%  0.0%  0.0%  B16..8:  0.2%  0.0%  0.0%  direct: 0.0%  skip:99.8%  L0:25.1% L1:74.9% BI: 0.0%
[libx264 @ 0x1d966a0] 8x8 transform intra:63.6% inter:75.9%
[libx264 @ 0x1d966a0] coded y,uvDC,uvAC intra: 61.5% 53.4% 24.4% inter: 0.5% 0.5% 0.0%
[libx264 @ 0x1d966a0] i16 v,h,dc,p: 52% 19% 19% 11%
[libx264 @ 0x1d966a0] i8 v,h,dc,ddl,ddr,vr,hd,vl,hu: 32% 17% 13%  4%  6%  9%  5%  8%  6%
[libx264 @ 0x1d966a0] i4 v,h,dc,ddl,ddr,vr,hd,vl,hu: 30% 18% 14%  5%  8% 10%  6%  6%  3%
[libx264 @ 0x1d966a0] i8c dc,h,v,p: 55% 17% 24%  4%
[libx264 @ 0x1d966a0] Weighted P-Frames: Y:0.0% UV:0.0%
[libx264 @ 0x1d966a0] ref P L0: 82.5% 13.2%  4.0%  0.3%
[libx264 @ 0x1d966a0] ref B L0: 60.2% 39.2%  0.6%
[libx264 @ 0x1d966a0] ref B L1: 98.5%  1.5%
[libx264 @ 0x1d966a0] kb/s:4327.77

回答1:

As your input file report a strange frame rate value 1k fps coming from the tbs and tbr value (look here for their definition)

the encoder generate a different result, 16k tbn, 1k tbc (default)

So by calling :

ffmpeg -fflags +genpts -i 1.webm -r 24 1.mp4

You configure ffmpeg to generate new pts (a/k.a Presentation TimeStamp) for each frame and you set the target frame-rate to 24.

So your output mp4 file info (ffmpeg -i ....) change from

Stream #0:0(eng): Video: h264 (High) (avc1 / 0x31637661), yuv420p, 1280x720 [SAR 1:1 DAR 16:9], 4327 kb/s, 1000.09 fps, 1k tbr, 16k tbn, 2k tbc

to

Stream #0:0(eng): Video: h264 (High) (avc1 / 0x31637661), yuv420p, 1280x720 [SAR 1:1 DAR 16:9], 1670 kb/s, 24 fps, 24 tbr, 12288 tbn, 48 tbc