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• Converting series of images with ffmpeg results in black video [migrated]

  27 avril 2013, par Marco Gagliardi

  I've just downloaded ffmpeg since it seems to perfectly match my needs (make a video from a set of pictures). I'm currently playing around with some examples just to get started and there's something weird happening that I can't explain.
  I'm trying this command (provided in the official documentation) :

  ffmpeg -f image2 -pattern_type glob -i 'foo-*.jpeg' -r 12 -s WxH foo.avi

  on a data set of 10 jpg pictures (of course I changed the pattern with '*.jpg'). The video seems to be encoded correctly but it's simply too fast to be sure about that (anyway it stops on the last frame that corresponds to the last picture). In order to get a longer video i thought to low the frame rate from 12 to 1 (one sec each picture) or 0.5 (2 sec each one) and so on.. no way ! with low rate values even if the video is played the pictures are simply not displayed. The player (VLC in my case) just shows a blank/empty video for a few seconds.

  Am I making something wrong or have I misunderstood the -r parameter ? Is it something related to codecs involved ? Finally.. How can i get each picture displayed for 1 or 2 seconds ?

  Here's the output :

  MacBook-Pro$ ffmpeg -f image2 -pattern_type glob -i '*.jpg' -r 1 -s 200x300 foo.avi
  
  ffmpeg version N-52517-g1e4f75d Copyright (c) 2000-2013 the FFmpeg developers
  
    built on Apr 27 2013 19:41:11 with llvm-gcc 4.2.1 (LLVM build 2336.11.00)
  
    configuration: --disable-yasm
  
    libavutil      52. 27.101 / 52. 27.101
  
    libavcodec     55.  6.100 / 55.  6.100
  
    libavformat    55.  3.100 / 55.  3.100
  
    libavdevice    55.  0.100 / 55.  0.100
  
    libavfilter     3. 61.100 /  3. 61.100
  
    libswscale      2.  2.100 /  2.  2.100
  
    libswresample   0. 17.102 /  0. 17.102
  
  Input #0, image2, from '*.jpg':
  
    Duration: 00:00:00.40, start: 0.000000, bitrate: N/A
  
      Stream #0:0: Video: mjpeg, yuvj422p, 2560x1920 [SAR 1:1 DAR 4:3], 25 fps, 25 tbr, 25 tbn, 25 tbc
  
  File 'foo.avi' already exists. Overwrite ? [y/N] y
  
  Output #0, avi, to 'foo.avi':
  
    Metadata:
  
      ISFT            : Lavf55.3.100
  
      Stream #0:0: Video: mpeg4 (FMP4 / 0x34504D46), yuv420p, 200x300 [SAR 2:1 DAR 4:3], q=2-31, 200 kb/s, 1 tbn, 1 tbc
  
  Stream mapping:
  
    Stream #0:0 -> #0:0 (mjpeg -> mpeg4)
  
  Press [q] to stop, [?] for help
  
  frame=    2 fps=0.0 q=2.0 Lsize=      43kB time=00:00:02.00 bitrate= 177.1kbits/s dup=0 drop=8    
  
  video:38kB audio:0kB subtitle:0 global headers:0kB muxing overhead 15.099197%
  
  MacBook-Pro$ 

• What do these two parts of libavcodec/h263data.h do exactly ?

  5 avril 2013, par Chris Lindgren

  Below are two segments of code from the FFMPEG library, specifically located here : libavcodec/h263data.h (http://ffmpeg.org/doxygen/0.6/h263data_8h-source.html).

  I would like to know more about how these two segments operate in the larger context of the codec library. Below, after these examples, I describe my understanding thus far and provide two clearer questions that I would like answers on.

  Thank you for any help !

  EXAMPLE 1

  00035 /* intra MCBPC, mb_type = (intra), then (intraq) */
  
  00036 const uint8_t ff_h263_intra_MCBPC_code[9] = { 1, 1, 2, 3, 1, 1, 2, 3, 1 };
  
  00037 const uint8_t ff_h263_intra_MCBPC_bits[9] = { 1, 3, 3, 3, 4, 6, 6, 6, 9 };

  AND EXAMPLE 2

  00039 /* inter MCBPC, mb_type = (inter), (intra), (interq), (intraq), (inter4v) */
  
  00040 /* Changed the tables for interq and inter4v+q, following the standard ** Juanjo ** */
  
  00041 const uint8_t ff_h263_inter_MCBPC_code[28] = {
  
  00042     1, 3, 2, 5,
  
  00043     3, 4, 3, 3,
  
  00044     3, 7, 6, 5,
  
  00045     4, 4, 3, 2,
  
  00046     2, 5, 4, 5,
  
  00047     1, 0, 0, 0, /* Stuffing */
  
  00048     2, 12, 14, 15,
  
  00049 };

  I understand that we're looking at a small part of the larger library of compression algorithms that affect orthogonal schemes, which predict the “correct,” or more aptly put, "original" inter- or intra-motion vectors, which are represented here in the names "ff_h263_inter_MCBPC_code," "ff_h263_intra_MCBPC_code," and "ff_h263_intra_MCBPC_bits."

  I know that the names in these two blocks of code demarcate the following :

  1. const refers to the declaration of a read only variable that can still be used outside of its scope like any other variable. The difference, stated in another way, is that the values in this array cannot be changed by any methods called outside of itself.

  2. uint8_t is an unsigned integer with a length of 8 bits that is part of a C99 standard, which is called "fixed width integer types." This particular type, an “exact width integer,” computes a range of signed or unsigned bits with a minimum value of 0 and a maximum value of 8, (i.e., the 8x8 macroblocks), which guarantees this number of bits across platforms, whether, let's say, 32-bit or 64-bit operating systems. (I researched this bit here : “Fixed width integer types” http://en.wikipedia.org/wiki/Stdint.h#stdint.h)

  3. MCBPC refers to Macroblock Type & Coded Block Pattern for Chrominance, but I don't fully understand the exact role of these particular arrays are in the scheme of the file and libavcodec. I understand more conceptually, than I do the details/number values defined in these examples.

  So, considering this, here's what I would like to know more about :

  1. Is my understanding, thus far, off in any way ?

  2. Can someone help breakdown what each code segment does ? more specifically, what do these number values signify/do in each case ?

  3. What does "Stuffing" mean ?

  Thank you, again, for any help in this matter !

• Reg-Video Rotation Metadata

  16 octobre 2013, par user2882101

  If I use :

  ffmpeg -i in.mov -vf "transpose=1" out.mov

  All mov files are getting rotated, but what I need is to automatically detect just the rotated videos and change orientation for just those videos. Please help.

  How can I automatically detect the rotation or orientation of the video during upload and rotate if needed, so that all mov files play in the correct orientation ?

  How can I get that metadata of current degree rotation of my video ?