Sur d’autres sites (6542)

• Convert WebM/H.264 to MP4/H.264 efficiently with ffmpeg.js

  31 juillet 2017, par SB2055

  As a result of the answer here : Recording cross-platform (H.264 ?) videos using WebRTC MediaRecorder

  How can one go about using ffmpeg.js to efficiently unwrap a webm h.264 video and re-wrap it into an mp4 container ?

  I’m looking through the docs : https://github.com/Kagami/ffmpeg.js?files=1

  However I don’t see (or perhaps I’m looking for the wrong terminology) any examples for the above. This operation will be performed on the browser (chrome) prior to uploading as a Blob - I could use a web worker though hopefully rewrapping is a trivial enough operation to not require it.

• Trying to compile x264 and ffmpeg for iPhone - "missing required architecture arm in file"

  4 août 2012, par jtrim

  I'm trying to compile x264 for use in an iPhone application. I see there are instructions on how to compile ffmpeg for use on the platform here : http://lists.mplayerhq.hu/pipermail/ffmpeg-devel/2009-October/076618.html , but I can't seem to find anything this complete for compiling x264 on the iPhone. I've found this source tree : http://gitorious.org/x264-arm that seems to have support for the ARM platform.

  Here is my config line :

  ./configure —cross-prefix=/usr/bin/ —host=arm-apple-darwin10 —extra-cflags="-B /Developer/Platforms/iPhoneOS.platform/Developer/SDKs/iPhoneOS3.2.sdk/usr/lib/ -I /Developer/Platforms/iPhoneOS.platform/Developer/SDKs/iPhoneOS3.2.sdk/usr/lib/"
  

  ...and inside configure I'm using the gas-preprocessor script (first link above) as my assembler :

  gas-preprocessor.pl gcc
  

  When I start compiling, it chunks away for a little while, then it spits out these warnings and a huge list of undefined symbols :

  ld : warning : option -s is obsolete and being ignored
  ld : warning : -force_cpusubtype_ALL will become unsupported for ARM architectures
  ld : warning : in /usr/lib/crt1.o, missing required architecture arm in file
  ld : warning : in /usr/X11R6/lib/libX11.dylib, missing required architecture arm in file
  ld : warning : in /usr/lib/libm.dylib, missing required architecture arm in file
  ld : warning : in /usr/lib/libpthread.dylib, missing required architecture arm in file
  ld : warning : in /usr/lib/libgcc_s.1.dylib, missing required architecture arm in file
  ld : warning : in /usr/lib/libSystem.dylib, missing required architecture arm in file
  Undefined symbols :
  

  My guess would be that the problem has to do with the "missing required architecture arm in file" warning...any ideas ?

• Create a mkv file with colored background and containing a given audio and subtitle stream

  25 mai 2023, par rdrg109

  Table of contents

  


  

  • The context

  


  • Minimal working example

  


  • What I've tried

    

    • Create a mkv file with colored background and an audio stream

    


    • Create a mkv file with colored background, an audio stream and a subtitles stream

    


    


  


  • The question

  


  


  


  The context

  


  I have a *.flac file and a *.srt file. I want to merge those files in a MKV file, but at the same time, I want to add a video stream. I want the video stream to show a green background the entire time.

  


  


  Minimal working example

  


  For our experimentation, let's create two sample files : one *.flac file and one *.srt file.

  


  The following command creates a *.flac file that lasts 60 seconds and contains a sine wave.

  


  $ ffmpeg -y -f lavfi -i "sine=f=1000:d=60" input.flac


  


  The following command creates a *.srt file. Note that our last subtitle lasts until the sixth second, this is intended.

  


  $ cat << EOF > input.srt
1
00:00:00,000 --> 00:00:03,000
This is the first subtitle in a
SRT file.

2
00:00:03,000 --> 00:00:06,000
This is the second subtitle in a
SRT file.
EOF


  


  


  What I've tried

  


  


  Create a mkv file with colored background and an audio stream

  


  I know how to create a MKV file containing a given audio stream and a colored background as the video stream.

  


  The following command creates a MKV file containing input.flac as the audio stream and green background as the video stream. The MKV file have the same duration as input.flac.

  


  $ ffmpeg \
  -y \
  -f lavfi \
  -i color=c=green:s=2x2 \
  -i input.flac \
  -c:v libx264 \
  -c:a copy \
  -shortest \
  output.mkv


  


  The following command shows the duration of the streams in the resulting file.

  


  $ ffprobe -v error -print_format json -show_entries stream=codec_type:stream_tags=duration output.mkv | jq -r ''


  


  {
  "programs": [],
  "streams": [
    {
      "codec_type": "video",
      "tags": {
        "DURATION": "00:00:58.200000000"
      }
    },
    {
      "codec_type": "audio",
      "tags": {
        "DURATION": "00:01:00.000000000"
      }
    }
  ]
}


  


  


  Create a mkv file with colored background, an audio stream and a subtitles stream

  


  To add a subtitles stream, I just need to specify the *.srt file. However, when I do this, the duration of the video is set to the time of the last subtitle in the *.srt file. This is expected because I have used -shortest. I would get the result I'm looking for if it were possible to specify the stream that -shortest gives top priority to. I haven't found this information on the Internet.

  


  $ ffmpeg \
  -y \
  -f lavfi \
  -i color=c=green:s=2x2 \
  -i input.flac \
  -i input.srt \
  -c:v libx264 \
  -c:a copy \
  -shortest \
  output.mkv


  


  The following command shows the duration of the streams in the resulting file. Note that the maximum duration of the resulting file is 6 seconds, while in the resulting file from the previous section it was 1 minute.

  


  $ ffprobe -v error -print_format json -show_entries stream=codec_type:stream_tags=duration output.mkv | jq -r ''


  


  {
  "programs": [],
  "streams": [
    {
      "codec_type": "video",
      "tags": {
        "DURATION": "00:00:01.160000000"
      }
    },
    {
      "codec_type": "audio",
      "tags": {
        "DURATION": "00:00:03.134000000"
      }
    },
    {
      "codec_type": "subtitle",
      "tags": {
        "DURATION": "00:00:06.000000000"
      }
    }
  ]
}


  


  


  The question

  


  Given a *.flac file and a *.srt file. How to merge them in a *.mkv file so that it has the *.flac file as the audio stream, the *.srt file as the subtitles stream and a green background as the video stream ?