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• ffmpeg concatenating videos of different fps while keeping the total length not changed

  23 novembre 2017, par A_Matar

  I wanna pad an mp4 video stream with another video clip of a static image that I created using :

  def generate_white_vid (duration):
  
      output_filename = os.path.join(p_path,'white_vid_'+" 0:.2f}".format(duration)+'.mp4')
  
      ffmpeg_create_vid_from_static_img = 'ffmpeg -loop 1 -i /path/WhiteBackground.jpg -c:v libx264 -t %f -pix_fmt yuv420p -vf scale=1920:1080 %s' % (duration, output_filename)
  
      p = subprocess.Popen(ffmpeg_create_vid_from_static_img, shell=True)
  
      p.communicate()
  
      return output_filename

  I use the following to concatenate :

  def concat_vids(clip_paths):
  
      filenames_txt = open('clips_to_join.txt','w')
  
      for clip in clip_paths:
  
          filenames_txt.write ('file \''+ clip+'\'\n')
  
      filenames_txt.close()
  
      output_filename = clip_paths[0].split('.', 2)[0]
  
      output_file_path = os.path.join(root_path, output_filename+'-padded.mp4')
  
      # join the clips
  
      ffmpeg_command = ["ffmpeg", "-f", "concat", "-safe", "0", "-i", "clips_to_join.txt", "-codec", "copy", output_file_path] # output_filename = ch0X-start_time-end_time
  
      p = subprocess.Popen(ffmpeg_command)
  
      p.communicate() # wait till the subprocess finishes. You can send commands to process as well.
  
      return output_file_path

  When I check the length of the resulting video after concatenation, I find that it is not equal to the sum of the two segments that I concatenated, and sometimes it is even less by some seconds !!

  Here is how I get the video length in seconds :

  def ffmpeg_len(vid_path):
  
      '''
  
      Returns length in seconds using ffmpeg
  
      '''
  
      ffmpeg_get_mediafile_length = ['sh', '-c', 'ffmpeg -i "$1" 2>&1 | grep Duration', '_', vid_path]
  
      p = subprocess.Popen(ffmpeg_get_mediafile_length, stdout=subprocess.PIPE, stderr=subprocess.PIPE)    
  
      output, err = p.communicate()
  
      length_regexp = 'Duration: (\d{2}):(\d{2}):(\d{2})(\.\d+),'
  
      re_length = re.compile(length_regexp)
  
      matches = re_length.search(output)
  
      if matches:
  
          video_length = int(matches.group(1)) * 3600 + \
  
                          int(matches.group(2)) * 60 + \
  
                          int(matches.group(3)) + float(matches.group(4))
  
          return video_length
  
      else:
  
          print("Can't determine video length.")
  
          print err
  
          raise SystemExit

  My guess is that maybe the concatenation unifies the fps rate for the all the clips to be joined, if this is the case, how to prevent this from happening ? How can I get a video of the desired length exactly.

  Maybe it worth mentioning that the video to padded is very short 0.42 second, the original video is 210.58 and the resultant video is 210.56 !

  I have verified that ffmpeg does generate the desired padding region and it is of the desired length 0.42 I got a 0.43 segment when I forced 30 fps but it is okay.

• How to force specific AVInputFormat in code (FFMPEG) ?

  18 février 2020, par kugipark

  ++Plaease understand that maybe some words or sentences could not be correct English.++

  I’m novice programmer and developing a video player app for Android which can play 5ch .avi video from http. It based on ffplay.c in FFMPEG libarary.

  Currently I have 2 problems for this below. It has occured only in android devices.

  ---

  1) Too much time taken for detecting format.

  • opening and finding stream info takes more than a minute when I trying to open 5ch video source whereas normal .mp4 (h264) source open almost immediately.

  2) Demuxing is too slow when it comes to large size video.

  • If the resolution of video getting larger, then displaying frame rate getting slower even though there are enough memory, network and CPU resources physically.

  To resolve my problem, I tried to force the format and decoders but I couldn’t found some information for specifying the input source in code level.
  The official doc site only refers to a sentence about those parameters like "If non-NULL, this parameter forces a specific input format. Otherwise the format is autodetected.". So I don’t have any clues how to set the number of streams, decoders, decoders’ private options, and etc. (And also which parameters should I manage.) If someone knows how to set the options(like AVDictionary), and pass to the av functions, please let me know an exmple. The source contains 2 video streams, 1 audio stream, and 2 more extra streams (for custom data like gps). The stream information of video is below. I printed it manually, and these are auto-detected information.

      ---------- File format information ----------
  
  flags=2097152
  
  video_codec_id=0 (NONE)
  
  audio_codec_id=0 (NONE)
  
  ctx_flags=0
  
  data_codec_id=0 (NONE)
  
  format_whitelist=(null)
  
  iformat=0xa19d0d2c
  
  ---------- Stream information ----------
  
  stream 1 of 5:
  
  ----- common ----------
  
  bit_rate: 11383235
  
  bits_per_coded_sample: 24
  
  bits_per_raw_sample: 0
  
  codec_id: 0x1C (H264)
  
  codec_tag: 875967048
  
  extradata_size: 0
  
  level: -99
  
  profile: -99
  
  sample_rate: 0
  
  ----- Video Stream ----------
  
  chroma_location: 0
  
  color_primaries: 2
  
  color_space: 2
  
  color_trc: 2
  
  field_order: 0
  
  format: -1 (NONE)
  
  height: 1080
  
  width: 1920
  
  sample_aspect_ratio.den: 1
  
  sample_aspect_ratio.num: 0
  
  video_delay: 0
  
  ----------------------------------------
  
  stream 2 of 5:
  
  ----- common ----------
  
  bit_rate: 6185438
  
  bits_per_coded_sample: 24
  
  bits_per_raw_sample: 0
  
  codec_id: 0x1C (H264)
  
  codec_tag: 875967048
  
  extradata_size: 0
  
  level: -99
  
  profile: -99
  
  sample_rate: 0
  
  ----- Video Stream ----------
  
  chroma_location: 0
  
  color_primaries: 2
  
  color_space: 2
  
  color_trc: 2
  
  field_order: 0
  
  format: -1 (NONE)
  
  height: 720
  
  width: 1280
  
  sample_aspect_ratio.den: 1
  
  sample_aspect_ratio.num: 0
  
  video_delay: 0
  
  ----------------------------------------
  
  stream 3 of 5:
  
  ----- common ----------
  
  bit_rate: 352800
  
  bits_per_coded_sample: 16
  
  bits_per_raw_sample: 0
  
  codec_id: 0x10000 (PCM_S16LE)
  
  codec_tag: 1
  
  extradata_size: 0
  
  level: -99
  
  profile: -99
  
  sample_rate: 22050
  
  ----- Audio Stream ----------
  
  block_align: 2
  
  channels: 1
  
  channel_layout: 0
  
  color_range: 0
  
  frame_size: 0
  
  initial_padding: 0
  
  seek_preroll: 0
  
  trailing_padding: 0
  
  ----------------------------------------
  
  stream 4 of 5:
  
  ----- common ----------
  
  bit_rate: 15625
  
  bits_per_coded_sample: 0
  
  bits_per_raw_sample: 0
  
  codec_id: 0x0 (NONE)
  
  codec_tag: 0
  
  extradata_size: 0
  
  level: -99
  
  profile: -99
  
  sample_rate: 0
  
  ----- Subtitle Stream ----------
  
  ----------------------------------------
  
  stream 5 of 5:
  
  ----- common ----------
  
  bit_rate: 33862
  
  bits_per_coded_sample: 0
  
  bits_per_raw_sample: 0
  
  codec_id: 0x0 (NONE)
  
  codec_tag: 0
  
  extradata_size: 0
  
  level: -99
  
  profile: -99
  
  sample_rate: 0
  
  ----- Subtitle Stream ----------

• examples : Add a VA-API encode example.

  6 novembre 2017, par Jun Zhao

  examples : Add a VA-API encode example.
  Supports only raw NV12 input.
  Example use :
  
  ./vaapi_encode 1920 1080 test.yuv test.h264
  Signed-off-by : Jun Zhao <jun.zhao@intel.com>
  
  Signed-off-by : Liu, Kaixuan <kaixuan.liu@intel.com>
  
  Signed-off-by : Mark Thompson <sw@jkqxz.net>
  

  • [DH] configure
  • [DH] doc/examples/Makefile
  • [DH] doc/examples/vaapi_encode.c