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• Edit H264 video stream header information ("start_pts" and "start_time")

  27 juin 2020, par David

  I have a video clip that appears to be slightly corrupted. Does not play on VLC but works on Potplayer. I used FFprobe to get information on the video.

  


  The problem appears to be with the start points of the video stream :

  


  time_base=1/90000
start_pts=585050940
start_time=6500.566000
duration_ts=585050940
duration=6500.566000
bit_rate=3123218


  


  I'm just wondering whether it is possible to manually edit the "start_pts" and "start_time" to 0 ? Is there any specific software to do this ? Due to large size of video file, I couldn't load it in Notepad++.

  


  Full ffprobe output shown below :

  


  # ffprobe output

[streams.stream.0]
index=0
codec_name=h264
codec_long_name=H.264 / AVC / MPEG-4 AVC / MPEG-4 part 10
profile=unknown
codec_type=video
codec_time_base=1/60
codec_tag_string=avc1
codec_tag=0x31637661
width=1920
height=1080
coded_width=1920
coded_height=1080
closed_captions=0
has_b_frames=0
sample_aspect_ratio=N/A
display_aspect_ratio=N/A
pix_fmt=unknown
level=-99
color_range=unknown
color_space=unknown
color_transfer=unknown
color_primaries=unknown
chroma_location=unspecified
field_order=unknown
timecode=N/A
refs=1
is_avc=true
nal_length_size=4
id=N/A
r_frame_rate=30/1
avg_frame_rate=30/1
time_base=1/90000
start_pts=585050940
start_time=6500.566000
duration_ts=585050940
duration=6500.566000
bit_rate=3123218
max_bit_rate=N/A
bits_per_raw_sample=N/A
nb_frames=195017
nb_read_frames=N/A
nb_read_packets=N/A

[streams.stream.0.disposition]
default=1
dub=0
original=0
comment=0
lyrics=0
karaoke=0
forced=0
hearing_impaired=0
visual_impaired=0
clean_effects=0
attached_pic=0
timed_thumbnails=0

[streams.stream.0.tags]
language=und
handler_name=VideoHandler

[streams.stream.1]
index=1
codec_name=aac
codec_long_name=AAC (Advanced Audio Coding)
profile=LC
codec_type=audio
codec_time_base=1/48000
codec_tag_string=mp4a
codec_tag=0x6134706d
sample_fmt=fltp
sample_rate=48000
channels=2
channel_layout=stereo
bits_per_sample=0
id=N/A
r_frame_rate=0/0
avg_frame_rate=0/0
time_base=1/48000
start_pts=0
start_time=0.000000
duration_ts=312029184
duration=6500.608000
bit_rate=189376
max_bit_rate=189376
bits_per_raw_sample=N/A
nb_frames=304718
nb_read_frames=N/A
nb_read_packets=N/A

[streams.stream.1.disposition]
default=1
dub=0
original=0
comment=0
lyrics=0
karaoke=0
forced=0
hearing_impaired=0
visual_impaired=0
clean_effects=0
attached_pic=0
timed_thumbnails=0

[streams.stream.1.tags]
language=eng
handler_name=SoundHandler

[format]
filename=D\:\\Start\\test.mp4
nb_streams=2
nb_programs=0
format_name=mov,mp4,m4a,3gp,3g2,mj2
format_long_name=QuickTime / MOV
start_time=0.000000
duration=6500.608000
size=2703218140
bit_rate=3326726
probe_score=100

[format.tags]
major_brand=isom
minor_version=512
compatible_brands=isomiso2avc1mp41


  


• FFmpeg "movflags" > "faststart" causes av_write_trailer() to return -2

  30 juin 2016, par williamtroup

  I’m setting up the format layout for the ideo as follows :

  AVOutputFormat* outputFormat = ffmpeg.av_guess_format(null, "output.mp4", null);
  
  
  
  AVCodec* videoCodec = ffmpeg.avcodec_find_encoder(outputFormat->video_codec);
  
  
  
  AVFormatContext* formatContext = ffmpeg.avformat_alloc_context();
  
  formatContext->oformat = outputFormat;
  
  formatContext->video_codec_id = videoCodec->id;
  
  
  
  ffmpeg.avformat_new_stream(formatContext, videoCodec);

  This is how I am setting up the Codec Context :

  AVCodecContext* codecContext = ffmpeg.avcodec_alloc_context3(videoCodec);
  
  codecContext->bit_rate = 400000;
  
  codecContext->width = 1280;
  
  codecContext->height = 720;
  
  codecContext->gop_size = 12;
  
  codecContext->max_b_frames = 1;
  
  codecContext->pix_fmt = videoCodec->pix_fmts[0];
  
  codecContext->codec_id = videoCodec->id;
  
  codecContext->codec_type = videoCodec->type;
  
  codecContext->time_base = new AVRational
  
  {
  
      num = 1,
  
      den = 30
  
  };

  I’m using the following code to setup the "movflags" > "faststart" option for the header of the video :

  AVDictionary* options = null;
  
  
  
  int result = ffmpeg.av_dict_set(&options, "movflags", "faststart", 0);
  
  
  
  int writeHeaderResult = ffmpeg.avformat_write_header(formatContext, &options);

  The file is opened and the header is written as follows :

  if ((formatContext->oformat->flags & ffmpeg.AVFMT_NOFILE) == 0)
  
  {
  
      int ioOptionResult = ffmpeg.avio_open(&formatContext->pb, "output.mp4", ffmpeg.AVIO_FLAG_WRITE);
  
  }
  
  
  
  int writeHeaderResult = ffmpeg.avformat_write_header(formatContext, &options);

  After this, I write each video frame as follows :

  outputFrame->pts = frameIndex;
  
  
  
  packet.flags |= ffmpeg.AV_PKT_FLAG_KEY;
  
  packet.pts = frameIndex;
  
  packet.dts = frameIndex;
  
  
  
  int encodedFrame = 0;
  
  int encodeVideoResult = ffmpeg.avcodec_encode_video2(codecContext, &packet, outputFrame, &encodedFrame);
  
  
  
  if (encodedFrame != 0)
  
  {
  
      packet.pts = ffmpeg.av_rescale_q(packet.pts, codecContext->time_base, m_videoStream->time_base);
  
      packet.dts = ffmpeg.av_rescale_q(packet.dts, codecContext->time_base, m_videoStream->time_base);
  
      packet.stream_index = m_videoStream->index;
  
  
  
      if (codecContext->coded_frame->key_frame > 0)
  
      {
  
          packet.flags |= ffmpeg.AV_PKT_FLAG_KEY;
  
      }
  
  
  
      int writeFrameResult = ffmpeg.av_interleaved_write_frame(formatContext, &packet);
  
  }

  After that, I write the trailer :

  int writeTrailerResult = ffmpeg.av_write_trailer(formatContext);

  However, writeTrailerResult is always -2. I’m been looking into this problem for days and cannot figure out what the problem is.

  The DLLs used for the AutoGen library are :

  avcodec-56.dll
  
  avdevice-56.dll
  
  avfilter-5.dll
  
  avformat-56.dll
  
  avutil-54.dll
  
  postproc-53.dll
  
  swresample-1.dll
  
  swscale-3.dll

• cut hls files in to many small ".ts" files or keep one big ".ts" file. which is better ?

  5 août 2022, par Evan Lee

  I need to stream my videos using HLS bytes range HTTP requests.

  


  FFmpeg has an option to keep all the ts file to one single large ".ts" file.

  


  Any pros and cons of split the ts files or keep a big ts file ?

  


  Is a big ts file make the request slower ? because of HDD fseek is slow ?