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• Révision 22135 : remplacement des http://doc.spip.org par http://code.spip.net (Francky)

  10 mai 2015, par erational@erational.org

  passage du copyright en 2015

• Non-monotonous DTS in output for audio stream using ffmpeg concat

  24 mai 2015, par Apollo Marquis

  This was asked in FFMPEG - Non-Monotonous DTS on concat. But the poster simply opted for MP4Box after getting no reply. However, I would like to stick with ffmpeg which I think is quicker.

  I am concatenating files from a text file list of mp4 files that have been encoded at the same time using the same codecs so there should be no incompatibility between the files.

  I am not even sure what Non-monotonous DTS is (anyone ?) but I am worried it may produce some glitches in the concatenated files. They seem ok but there is some evidence of artefacts in the sound. Can I tweak my command line to get rid of this error, and will it speed up the concatenation process ?
  I am using Python subprocess call and the file passed into this function is the list of files. The function decorator is just a timer function for profiling.
  I have tried this with my system ffmpeg not just the static build, and it has the same problem.

  @fn_timer
  
  def concat(file):
  
      proc = call(['/opt/jane_ng/jane_nodejs/ffmpeg-git-20150308-64bit-static/ffmpeg', '-f', 'concat', '-i', file, '-c', 'copy', '-y', 'testConcat.mp4'])

  When I run this, I get the following output :

  ffmpeg version N-45007-g9d7e42e-   http://johnvansickle.com/ffmpeg/    Copyright (c) 2000-2015 the FFmpeg developers
  
    built with gcc 4.9.2 (Debian 4.9.2-10)
  
    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-aacenc --enable-libvo-amrwbenc --enable-gray --enable-libopenjpeg --enable-libopus --enable-libass --enable-gnutls --enable-libvidstab --cc=gcc-4.9
  
    libavutil      54. 20.100 / 54. 20.100
  
    libavcodec     56. 26.100 / 56. 26.100
  
    libavformat    56. 25.101 / 56. 25.101
  
    libavdevice    56.  4.100 / 56.  4.100
  
    libavfilter     5. 12.100 /  5. 12.100
  
    libswscale      3.  1.101 /  3.  1.101
  
    libswresample   1.  1.100 /  1.  1.100
  
    libpostproc    53.  3.100 / 53.  3.100
  
  [concat @ 0x31bdd80] Could not find codec parameters for stream 2 (Unknown: none): unknown codec
  
  Consider increasing the value for the 'analyzeduration' and 'probesize' options
  
  Input #0, concat, from '/opt/combinatoria/generator/concatFiles/concat.txt':
  
    Duration: N/A, start: 0.000000, bitrate: 1625 kb/s
  
      Stream #0:0: Video: h264 (Main) (avc1 / 0x31637661), yuv420p(tv), 960x540 [SAR 1:1 DAR 16:9], 1561 kb/s, 25 fps, 25 tbr, 90k tbn, 50 tbc
  
      Stream #0:1: Audio: aac (HE-AAC) (mp4a / 0x6134706D), 44100 Hz, stereo, fltp, 64 kb/s
  
      Stream #0:2: Unknown: none
  
  Output #0, mp4, to 'testConcat.mp4':
  
    Metadata:
  
      encoder         : Lavf56.25.101
  
      Stream #0:0: Video: h264 ([33][0][0][0] / 0x0021), yuv420p, 960x540 [SAR 1:1 DAR 16:9], q=2-31, 1561 kb/s, 25 fps, 25 tbr, 90k tbn, 90k tbc
  
      Stream #0:1: Audio: aac ([64][0][0][0] / 0x0040), 44100 Hz, stereo, 64 kb/s
  
  Stream mapping:
  
    Stream #0:0 -> #0:0 (copy)
  
    Stream #0:1 -> #0:1 (copy)
  
  Press [q] to stop, [?] for help
  
  [mp4 @ 0x3255080] Non-monotonous DTS in output stream 0:1; previous: 253952, current: 250488; changing to 253953. This may result in incorrect timestamps in the output file.
  
  [mp4 @ 0x3255080] Non-monotonous DTS in output stream 0:1; previous: 253953, current: 252536; changing to 253954. This may result in incorrect timestamps in the output file.
  
  [mp4 @ 0x3255080] Non-monotonous DTS in output stream 0:1; previous: 754296, current: 751464; changing to 754297. This may result in incorrect timestamps in the output file.
  
  [mp4 @ 0x3255080] Non-monotonous DTS in output stream 0:1; previous: 754297, current: 753512; changing to 754298. This may result in incorrect timestamps in the output file.
  
  [mp4 @ 0x3255080] Non-monotonous DTS in output stream 0:1; previous: 974696, current: 971964; changing to 974697. This may result in incorrect timestamps in the output file.
  
  [mp4 @ 0x3255080] Non-monotonous DTS in output stream 0:1; previous: 974697, current: 974012; changing to 974698. This may result in incorrect timestamps in the output file.
  
  [mp4 @ 0x3255080] Non-monotonous DTS in output stream 0:1; previous: 1340604, current: 1337112; changing to 1340605. This may result in incorrect timestamps in the output file.
  
  [mp4 @ 0x3255080] Non-monotonous DTS in output stream 0:1; previous: 1340605, current: 1339160; changing to 1340606. This may result in incorrect timestamps in the output file.
  
  [mp4 @ 0x3255080] Non-monotonous DTS in output stream 0:1; previous: 1746712, current: 1742832; changing to 1746713. This may result in incorrect timestamps in the output file.
  
  [mp4 @ 0x3255080] Non-monotonous DTS in output stream 0:1; previous: 1746713, current: 1744880; changing to 1746714. This may result in incorrect timestamps in the output file.
  
  [mp4 @ 0x3255080] Non-monotonous DTS in output stream 0:1; previous: 2119664, current: 2116800; changing to 2119665. This may result in incorrect timestamps in the output file.
  
  [mp4 @ 0x3255080] Non-monotonous DTS in output stream 0:1; previous: 2119665, current: 2118848; changing to 2119666. This may result in incorrect timestamps in the output file.
  
  [mp4 @ 0x3255080] Non-monotonous DTS in output stream 0:1; previous: 2274496, current: 2272032; changing to 2274497. This may result in incorrect timestamps in the output file.
  
  [mp4 @ 0x3255080] Non-monotonous DTS in output stream 0:1; previous: 2274497, current: 2274080; changing to 2274498. This may result in incorrect timestamps in the output file.
  
  [mp4 @ 0x3255080] Non-monotonous DTS in output stream 0:1; previous: 2685728, current: 2683044; changing to 2685729. This may result in incorrect timestamps in the output file.
  
  [mp4 @ 0x3255080] Non-monotonous DTS in output stream 0:1; previous: 2685729, current: 2685092; changing to 2685730. This may result in incorrect timestamps in the output file.
  
  [mp4 @ 0x3255080] Non-monotonous DTS in output stream 0:1; previous: 2850980, current: 2847096; changing to 2850981. This may result in incorrect timestamps in the output file.
  
  [mp4 @ 0x3255080] Non-monotonous DTS in output stream 0:1; previous: 2850981, current: 2849144; changing to 2850982. This may result in incorrect timestamps in the output file.
  
  [mp4 @ 0x3255080] Non-monotonous DTS in output stream 0:1; previous: 3033464, current: 3030552; changing to 3033465. This may result in incorrect timestamps in the output file.
  
  [mp4 @ 0x3255080] Non-monotonous DTS in output stream 0:1; previous: 3033465, current: 3032600; changing to 3033466. This may result in incorrect timestamps in the output file.
  
  [mp4 @ 0x3255080] Non-monotonous DTS in output stream 0:1; previous: 3384856, current: 3381588; changing to 3384857. This may result in incorrect timestamps in the output file.
  
  [mp4 @ 0x3255080] Non-monotonous DTS in output stream 0:1; previous: 3384857, current: 3383636; changing to 3384858. This may result in incorrect timestamps in the output file.
  
  [mp4 @ 0x3255080] Non-monotonous DTS in output stream 0:1; previous: 3760468, current: 3757320; changing to 3760469. This may result in incorrect timestamps in the output file.
  
  [mp4 @ 0x3255080] Non-monotonous DTS in output stream 0:1; previous: 3760469, current: 3759368; changing to 3760470. This may result in incorrect timestamps in the output file.
  
  [mp4 @ 0x3255080] Non-monotonous DTS in output stream 0:1; previous: 3990792, current: 3988404; changing to 3990793. This may result in incorrect timestamps in the output file.
  
  [mp4 @ 0x3255080] Non-monotonous DTS in output stream 0:1; previous: 3990793, current: 3990452; changing to 3990794. This may result in incorrect timestamps in the output file.
  
  [mp4 @ 0x3255080] Non-monotonous DTS in output stream 0:1; previous: 4295604, current: 4291812; changing to 4295605. This may result in incorrect timestamps in the output file.
  
  [mp4 @ 0x3255080] Non-monotonous DTS in output stream 0:1; previous: 4295605, current: 4293860; changing to 4295606. This may result in incorrect timestamps in the output file.
  
  [mp4 @ 0x3255080] Non-monotonous DTS in output stream 0:1; previous: 4750564, current: 4746924; changing to 4750565. This may result in incorrect timestamps in the output file.
  
  [mp4 @ 0x3255080] Non-monotonous DTS in output stream 0:1; previous: 4750565, current: 4748972; changing to 4750566. This may result in incorrect timestamps in the output file.
  
  [mp4 @ 0x3255080] Non-monotonous DTS in output stream 0:1; previous: 5025452, current: 5022108; changing to 5025453. This may result in incorrect timestamps in the output file.
  
  [mp4 @ 0x3255080] Non-monotonous DTS in output stream 0:1; previous: 5025453, current: 5024156; changing to 5025454. This may result in incorrect timestamps in the output file.
  
  [mp4 @ 0x3255080] Non-monotonous DTS in output stream 0:1; previous: 5271964, current: 5269068; changing to 5271965. This may result in incorrect timestamps in the output file.
  
  [mp4 @ 0x3255080] Non-monotonous DTS in output stream 0:1; previous: 5271965, current: 5271116; changing to 5271966. This may result in incorrect timestamps in the output file.
  
  [mp4 @ 0x3255080] Non-monotonous DTS in output stream 0:1; previous: 5707340, current: 5704776; changing to 5707341. This may result in incorrect timestamps in the output file.
  
  [mp4 @ 0x3255080] Non-monotonous DTS in output stream 0:1; previous: 5707341, current: 5706824; changing to 5707342. This may result in incorrect timestamps in the output file.
  
  [mp4 @ 0x3255080] Non-monotonous DTS in output stream 0:1; previous: 6003784, current: 6001128; changing to 6003785. This may result in incorrect timestamps in the output file.
  
  [mp4 @ 0x3255080] Non-monotonous DTS in output stream 0:1; previous: 6003785, current: 6003176; changing to 6003786. This may result in incorrect timestamps in the output file.
  
  [mp4 @ 0x3255080] Non-monotonous DTS in output stream 0:1; previous: 6371816, current: 6368040; changing to 6371817. This may result in incorrect timestamps in the output file.
  
  [mp4 @ 0x3255080] Non-monotonous DTS in output stream 0:1; previous: 6371817, current: 6370088; changing to 6371818. This may result in incorrect timestamps in the output file.
  
  [mp4 @ 0x3255080] Non-monotonous DTS in output stream 0:1; previous: 6875944, current: 6872544; changing to 6875945. This may result in incorrect timestamps in the output file.
  
  [mp4 @ 0x3255080] Non-monotonous DTS in output stream 0:1; previous: 6875945, current: 6874592; changing to 6875946. This may result in incorrect timestamps in the output file.
  
  [mp4 @ 0x3255080] Non-monotonous DTS in output stream 0:1; previous: 7042528, current: 7040124; changing to 7042529. This may result in incorrect timestamps in the output file.
  
  [mp4 @ 0x3255080] Non-monotonous DTS in output stream 0:1; previous: 7042529, current: 7042172; changing to 7042530. This may result in incorrect timestamps in the output file.
  
  [mp4 @ 0x3255080] Non-monotonous DTS in output stream 0:1; previous: 7314556, current: 7311780; changing to 7314557. This may result in incorrect timestamps in the output file.
  
  [mp4 @ 0x3255080] Non-monotonous DTS in output stream 0:1; previous: 7314557, current: 7313828; changing to 7314558. This may result in incorrect timestamps in the output file.
  
  [mp4 @ 0x3255080] Non-monotonous DTS in output stream 0:1; previous: 7541156, current: 7537572; changing to 7541157. This may result in incorrect timestamps in the output file.
  
  [mp4 @ 0x3255080] Non-monotonous DTS in output stream 0:1; previous: 7541157, current: 7539620; changing to 7541158. This may result in incorrect timestamps in the output file.
  
  [mp4 @ 0x3255080] Non-monotonous DTS in output stream 0:1; previous: 7795620, current: 7791588; changing to 7795621. This may result in incorrect timestamps in the output file.
  
  [mp4 @ 0x3255080] Non-monotonous DTS in output stream 0:1; previous: 7795621, current: 7793636; changing to 7795622. This may result in incorrect timestamps in the output file.
  
  [mp4 @ 0x3255080] Non-monotonous DTS in output stream 0:1; previous: 8063972, current: 8059716; changing to 8063973. This may result in incorrect timestamps in the output file.
  
  [mp4 @ 0x3255080] Non-monotonous DTS in output stream 0:1; previous: 8063973, current: 8061764; changing to 8063974. This may result in incorrect timestamps in the output file.
  
  [mp4 @ 0x3255080] Non-monotonous DTS in output stream 0:1; previous: 8063974, current: 8063812; changing to 8063975. This may result in incorrect timestamps in the output file.
  
  [mp4 @ 0x3255080] Non-monotonous DTS in output stream 0:1; previous: 8350532, current: 8347248; changing to 8350533. This may result in incorrect timestamps in the output file.
  
  [mp4 @ 0x3255080] Non-monotonous DTS in output stream 0:1; previous: 8350533, current: 8349296; changing to 8350534. This may result in incorrect timestamps in the output file.
  
  [mp4 @ 0x3255080] Non-monotonous DTS in output stream 0:1; previous: 8656496, current: 8652420; changing to 8656497. This may result in incorrect timestamps in the output file.
  
  [mp4 @ 0x3255080] Non-monotonous DTS in output stream 0:1; previous: 8656497, current: 8654468; changing to 8656498. This may result in incorrect timestamps in the output file.
  
  [mp4 @ 0x3255080] Non-monotonous DTS in output stream 0:1; previous: 8902276, current: 8899380; changing to 8902277. This may result in incorrect timestamps in the output file.
  
  [mp4 @ 0x3255080] Non-monotonous DTS in output stream 0:1; previous: 8902277, current: 8901428; changing to 8902278. This may result in incorrect timestamps in the output file.
  
  [mp4 @ 0x3255080] Non-monotonous DTS in output stream 0:1; previous: 9159476, current: 9156924; changing to 9159477. This may result in incorrect timestamps in the output file.
  
  [mp4 @ 0x3255080] Non-monotonous DTS in output stream 0:1; previous: 9159477, current: 9158972; changing to 9159478. This may result in incorrect timestamps in the output file.
  
  [mp4 @ 0x3255080] Non-monotonous DTS in output stream 0:1; previous: 9468220, current: 9465624; changing to 9468221. This may result in incorrect timestamps in the output file.
  
  [mp4 @ 0x3255080] Non-monotonous DTS in output stream 0:1; previous: 9468221, current: 9467672; changing to 9468222. This may result in incorrect timestamps in the output file.
  
  [mp4 @ 0x3255080] Non-monotonous DTS in output stream 0:1; previous: 9748248, current: 9744336; changing to 9748249. This may result in incorrect timestamps in the output file.
  
  [mp4 @ 0x3255080] Non-monotonous DTS in output stream 0:1; previous: 9748249, current: 9746384; changing to 9748250. This may result in incorrect timestamps in the output file.
  
  frame= 5637 fps=0.0 q=-1.0 Lsize=   45617kB time=00:03:45.60 bitrate=1656.4kbits/s    
  
  video:43701kB audio:1792kB subtitle:0kB other streams:0kB global headers:0kB muxing overhead: 0.272048%
  
  Total time running concat: 0.451297044754 seconds

  This process is absolutely key to my current project so any help or clarification would be really appreciated.

• Using ffmpeg to combine small mp4 chunks ?

  20 mai 2015, par shiny formica

  I’m trying to convert batches of png images into a single mp4 x264 video using ffmpeg. The conversion, for reasons I won’t go into, converts groups of frames into short mp4 chunks and then I want to take those chunks and merge them into the final video at a specific fps (in this case 30fps).

  My understanding of ffmpeg and the x264 options is too limited, and while I can produce the individual mp4 chunks from the source png frames without trouble, the final merge always ends up duplicating and/or dropping frames especially with very short chunks (< 4 frames).

  The conversion from png to mp4 uses this command :

  ffmpeg -start_number 1001 -framerate 30 -f image2 -i 'intermediate.%d.png' -c:v libx264 -crf 1 -pix_fmt yuv420p -movflags +faststart -frames:v 4 -r 30 chunk.1.mp4 -y

  which appears to work as expected, I get a playable mp4 chunk of, in this case, 4 frames of the sequence of png images at 30fps. The length of each chunk can be anywhere from 1 frame to around 100 frames.

  When all the chunks are generated, I’ve been trying to use the concat demuxer to combine without re-encoding, placing all the source chunk paths in a file :

  concat.txt :

  file 'chunk.1.mp4'
  
  file 'chunk.2.mp4'
  
  file 'chunk.3.mp4'
  
  ...

  and then running this ffmpeg command :

  ffmpeg -f concat -i concat.txt -c:v copy merged.mp4 -y

  but it says this during the concatenation :

  [concat @ 0x315ff80] Estimating duration from bitrate, this may be inaccurate

  and the resulting mp4 has dropped/duplicated frames. So I tried adding duration info to the concat.txt file :

  file 'chunk.1.mp4'
  
  duration 0.133333
  
  file 'chunk.2.mp4'
  
  duration 0.133333
  
  file 'chunk.3.mp4'
  
  duration 0.066666

  in this case, two 4-frame/30fps chunks and one 2-frame/30fps chunk. Which gets rid of that estimation warning, but the result is still duplicating/dropping frames.

  I’m not sure where I’m going wrong here...what do I need to do either in the production of the short mp4 segments, or in the combination stage, to get a single mp4 at the right framerate with no duplicated or dropped frames ?

  As suggested, here’s the console output for the conversion from png->mp4 chunks :

  ffmpeg -loglevel verbose -start_number 1001 -framerate 30 -f image2 -i 'intermediate.%d.png' -c:v libx264 -crf 1 -pix_fmt yuv420p -movflags +faststart -frames:v 4 -r 30 chunk.1.mp4 -y
  
  ffmpeg version 2.5.4 Copyright (c) 2000-2015 the FFmpeg developers
  
    built on Feb 26 2015 10:23:42 with gcc 4.4.7 (GCC) 20120313 (Red Hat 4.4.7-3)
  
    configuration: --prefix=/dept/srd/vendor/ffmpeg/bundle.rhel6/ffmpeg2.5.4 --enable-static --enable-pthreads --enable-gpl --enable-version3 --disable-ffserver --disable-ffplay --disable-ffprobe --enable-x11grab --enable-nonfree --extra-cflags=-I/dept/srd/vendor/ffmpeg/extern/rhel6/include --extra-ldflags=-L/dept/srd/vendor/ffmpeg/extern/rhel6/lib --enable-libx264 --enable-fontconfig --enable-libfreetype --enable-swscale --enable-libmp3lame --enable-libfaac --disable-yasm
  
    libavutil      54. 15.100 / 54. 15.100
  
    libavcodec     56. 13.100 / 56. 13.100
  
    libavformat    56. 15.102 / 56. 15.102
  
    libavdevice    56.  3.100 / 56.  3.100
  
    libavfilter     5.  2.103 /  5.  2.103
  
    libswscale      3.  1.101 /  3.  1.101
  
    libswresample   1.  1.100 /  1.  1.100
  
    libpostproc    53.  3.100 / 53.  3.100
  
  Input #0, image2, from 'intermediate.%d.png':
  
    Duration: 00:00:00.27, start: 0.000000, bitrate: N/A
  
      Stream #0:0: Video: png, rgba, 1024x1024 (0x0), 30 fps, 30 tbr, 30 tbn, 30 tbc
  
  [graph 0 input from stream 0:0 @ 0x273e9c0] w:1024 h:1024 pixfmt:rgba tb:1/30 fr:30/1 sar:0/1 sws_param:flags=2
  
  [auto-inserted scaler 0 @ 0x2737ea0] w:iw h:ih flags:'0x4' interl:0
  
  [format @ 0x273ece0] auto-inserting filter 'auto-inserted scaler 0' between the filter 'Parsed_null_0' and the filter 'format'
  
  [auto-inserted scaler 0 @ 0x2737ea0] w:1024 h:1024 fmt:rgba sar:0/1 -> w:1024 h:1024 fmt:yuv420p sar:0/1 flags:0x4
  
  [libx264 @ 0x273c540] using cpu capabilities: MMX2 SSE2Fast SSSE3 SSE4.2 AVX
  
  [libx264 @ 0x273c540] profile High, level 3.2
  
  [libx264 @ 0x273c540] 264 - core 142 - H.264/MPEG-4 AVC codec - Copyleft 2003-2014 - 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=36 lookahead_threads=6 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=1.0 qcomp=0.60 qpmin=0 qpmax=69 qpstep=4 ip_ratio=1.40 aq=1:1.00
  
  Output #0, mp4, to 'chunk.1.mp4':
  
    Metadata:
  
      encoder         : Lavf56.15.102
  
      Stream #0:0: Video: h264 (libx264) ([33][0][0][0] / 0x0021), yuv420p, 1024x1024, q=-1--1, 30 fps, 15360 tbn, 30 tbc
  
      Metadata:
  
        encoder         : Lavc56.13.100 libx264
  
  Stream mapping:
  
    Stream #0:0 -> #0:0 (png (native) -> h264 (libx264))
  
  Press [q] to stop, [?] for help
  
  No more output streams to write to, finishing.
  
  [mp4 @ 0x273baa0] Starting second pass: moving the moov atom to the beginning of the file
  
  frame=    4 fps=0.0 q=-1.0 Lsize=     197kB time=00:00:00.06 bitrate=24228.7kbits/s    
  
  video:196kB audio:0kB subtitle:0kB other streams:0kB global headers:0kB muxing overhead: 0.439751%
  
  Input file #0 (intermediate.%d.png):
  
    Input stream #0:0 (video): 8 packets read (2341016 bytes); 5 frames decoded; 
  
    Total: 8 packets (2341016 bytes) demuxed
  
  Output file #0 (chunk.3.mp4):
  
    Output stream #0:0 (video): 4 frames encoded; 4 packets muxed (201023 bytes); 
  
    Total: 4 packets (201023 bytes) muxed
  
  [libx264 @ 0x273c540] frame I:1     Avg QP: 0.47  size:116049
  
  [libx264 @ 0x273c540] frame P:1     Avg QP: 2.29  size: 37932
  
  [libx264 @ 0x273c540] frame B:2     Avg QP: 2.37  size: 23184
  
  [libx264 @ 0x273c540] consecutive B-frames: 25.0%  0.0% 75.0%  0.0%
  
  [libx264 @ 0x273c540] mb I  I16..4: 80.0%  4.5% 15.5%
  
  [libx264 @ 0x273c540] mb P  I16..4:  0.2%  0.1%  0.4%  P16..4:  8.1%  3.6%  3.7%  0.0%  0.0%    skip:83.9%
  
  [libx264 @ 0x273c540] mb B  I16..4:  0.0%  0.0%  0.0%  B16..8:  4.8%  1.2%  1.6%  direct: 4.3%  skip:88.1%  L0:38.6% L1:39.3% BI:22.1%
  
  [libx264 @ 0x273c540] 8x8 transform intra:4.6% inter:14.8%
  
  [libx264 @ 0x273c540] coded y,uvDC,uvAC intra: 20.7% 22.9% 22.8% inter: 8.7% 10.1% 10.0%
  
  [libx264 @ 0x273c540] i16 v,h,dc,p: 95%  1%  3%  1%
  
  [libx264 @ 0x273c540] i8 v,h,dc,ddl,ddr,vr,hd,vl,hu: 21% 21% 22%  6%  6%  6%  7%  5%  6%
  
  [libx264 @ 0x273c540] i4 v,h,dc,ddl,ddr,vr,hd,vl,hu: 20% 17% 18%  7%  8%  7%  8%  6%  8%
  
  [libx264 @ 0x273c540] i8c dc,h,v,p: 89%  4%  4%  3%
  
  [libx264 @ 0x273c540] Weighted P-Frames: Y:0.0% UV:0.0%
  
  [libx264 @ 0x273c540] ref B L1: 89.5% 10.5%
  
  [libx264 @ 0x273c540] kb/s:12020.88

  as I said, this appears to produce a valid mp4 at 30fps with no duplicated or dropped frames from the input images.

  Here’s the output of the combine phase :

  ffmpeg -loglevel verbose -f concat -i concat.txt -c:v copy merged.mp4 -y
  
  ffmpeg version 2.5.4 Copyright (c) 2000-2015 the FFmpeg developers
  
    built on Feb 26 2015 10:23:42 with gcc 4.4.7 (GCC) 20120313 (Red Hat 4.4.7-3)
  
    configuration: --prefix=/dept/srd/vendor/ffmpeg/bundle.rhel6/ffmpeg2.5.4 --enable-static --enable-pthreads --enable-gpl --enable-version3 --disable-ffserver --disable-ffplay --disable-ffprobe --enable-x11grab --enable-nonfree --extra-cflags=-I/dept/srd/vendor/ffmpeg/extern/rhel6/include --extra-ldflags=-L/dept/srd/vendor/ffmpeg/extern/rhel6/lib --enable-libx264 --enable-fontconfig --enable-libfreetype --enable-swscale --enable-libmp3lame --enable-libfaac --disable-yasm
  
    libavutil      54. 15.100 / 54. 15.100
  
    libavcodec     56. 13.100 / 56. 13.100
  
    libavformat    56. 15.102 / 56. 15.102
  
    libavdevice    56.  3.100 / 56.  3.100
  
    libavfilter     5.  2.103 /  5.  2.103
  
    libswscale      3.  1.101 /  3.  1.101
  
    libswresample   1.  1.100 /  1.  1.100
  
    libpostproc    53.  3.100 / 53.  3.100
  
  Input #0, concat, from 'concat.txt':
  
    Duration: 00:00:00.67, start: 0.000000, bitrate: 2 kb/s
  
      Stream #0:0: Video: h264 (High) (avc1 / 0x31637661), yuv420p, 1024x1024, 7791 kb/s, 30 fps, 30 tbr, 15360 tbn, 60 tbc
  
  Output #0, mp4, to 'merged.mp4':
  
    Metadata:
  
      encoder         : Lavf56.15.102
  
      Stream #0:0: Video: h264 ([33][0][0][0] / 0x0021), yuv420p, 1024x1024 (0x0), q=2-31, 7791 kb/s, 30 fps, 15360 tbn, 15360 tbc
  
  Stream mapping:
  
    Stream #0:0 -> #0:0 (copy)
  
  Press [q] to stop, [?] for help
  
  No more output streams to write to, finishing.
  
  frame=   20 fps=0.0 q=-1.0 Lsize=     748kB time=00:00:00.56 bitrate=10805.0kbits/s    
  
  video:746kB audio:0kB subtitle:0kB other streams:0kB global headers:0kB muxing overhead: 0.141687%
  
  Input file #0 (concat.txt):
  
    Input stream #0:0 (video): 20 packets read (764361 bytes); 
  
    Total: 20 packets (764361 bytes) demuxed
  
  Output file #0 (merged.mp4):
  
    Output stream #0:0 (video): 20 packets muxed (764361 bytes); 
  
    Total: 20 packets (764361 bytes) muxed