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• VLC syntax to transcode and stream to stdout ?

  19 novembre 2016, par Will Tower

  Goal : I am trying to use VLC as a local server to expand the video capabilities of an app created with Adobe AIR, Flex and Actionscript. I am using VLC to stream to stdoutand reading that output from within my app.

  VLC Streaming capabilities
  VLC Flash Video
  Stream VLC to Website with asf and Flash

  Status : I am able to launch VLC as a background process and control it through its remote control interface (more detail). I can load, transcode and stream a local video file. The example app below is a barebones testbed demonstrating this.

  Issue : I am getting data in to my app but it is not rendering as video. I don’t know if it is a problem with my VLC commands or with writing to/reading from stdout. This technique of reading from stdout in AIR works (with ffmpeg for example).

  One of the various transcoding commands I have tried :

  -I rc  // remote control interface  
  
  -vvv   // verbose debuging  
  
  --sout  // transcode, stream to stdout 
  
  "#transcode{vcodec=FLV1}:std{access=file,mux=ffmpeg{mux=flv},dst=-}"

  This results in data coming into to my app but for some reason it is not rendering as video when using appendBytes with the NetStream instance.

  If instead I write the data to an .flv file, a valid file is created – so the broken part seems to be writing it to stdout. One thing I have noticed : I am not getting metadata through the stdout`method. If I play the file created with the command below, I do see metadata.

  // writing to a file
  
  var output:File = File.desktopDirectory.resolvePath("stream.flv");
  
  var outputPath:String = output.nativePath;
  
  "#transcode{vcodec=FLV1}:std{access=file,mux=ffmpeg{mux=flv},dst=" + outputPath + "}");

  ---

  Hoping someone sees where I am going wrong here.

  ---

  Update 1 : Just to add some more detail (!) – I took a look at the .flv file that is generated to examine the metadata. It appears at the head of the file as shown below. I have the correct onMetaData handler set up and see a trace of this data if I play the file from disk. I do not see this trace when reading from stdout and NetStream is in Data Generation mode. Is it possible that it isn’t getting sent to stdout for some reason ? I’ve tried generating my own header and appending that before the stream starts – I may not have the header format correct.

  

  ---

  Update 2 : So in my AIR app I was able to crudely parse the incoming stdout stream coming from VLC. I wanted to see if the FLV header data was being sent – and it appears that it is. I don’t know if it is in the correct format, etc. but as I mention above, if I write to an .flv file instead of stdout, a valid .flv file is created.

  Completely at a loss now – have tried everything I could think of and followed up every web link I could find on the issues involved. Alas – so close and it would have been so cool to leverage VLC from within AIR.

• slicing and seeking extremeley small sections of video in ffmpeg

  20 février 2021, par Zarc Rowden

  I am writing a program that maps midi data to timestamps in a video. The end result is a kind of automatic generation of audio visuals for beat making or techno heads. The program takes in midi, slices a video into chunks based on the midi events and mappings and finally joins the slices into a video with 1:1 timing of monophonic midi notes to sections of a video.

  


  When it is successful, the result is very cool and watching the video jump around and lock in to midi notes is very interesting

  


  However, I am affraid that the ffmpeg commands I use are not giving exact results.

  


  The code I feed to ffmpeg looks like this

  


  EVENTS : left is midinote number, right is time from start of recording in which note occurs.

  


    [{"note"=>"start", "timestamp"=>0.0},
   {"note"=>48, "timestamp"=>0.5700000037904829},
   {"note"=>51, "timestamp"=>383.7100000018836},
   {"note"=>45, "timestamp"=>884.3500000002678},
   {"note"=>48, "timestamp"=>999.0449999968405},
   {"note"=>51, "timestamp"=>1383.544999996957},
   {"note"=>45, "timestamp"=>1884.2599999989034},
   {"note"=>48, "timestamp"=>1998.890000002575},
   {"note"=>51, "timestamp"=>2383.4199999982957},
   {"note"=>45, "timestamp"=>2884.1000000029453},
   {"note"=>48, "timestamp"=>2998.7200000032317},
   {"note"=>51, "timestamp"=>3383.2800000018324},
   {"note"=>45, "timestamp"=>3883.894999999029},
   {"note"=>48, "timestamp"=>3998.6250000001746},
   {"note"=>51, "timestamp"=>4384.550000002491},
   {"note"=>45, "timestamp"=>4883.780000003753},
   {"note"=>48, "timestamp"=>4998.404999998456},
   {"note"=>51, "timestamp"=>5384.39500000095},
   {"note"=>45, "timestamp"=>5883.565000003728},
   {"note"=>48, "timestamp"=>5998.464999996941},
   {"note"=>51, "timestamp"=>6384.254999997211},
   {"note"=>45, "timestamp"=>6883.4550000028685},
   {"note"=>48, "timestamp"=>6998.585000001185},
   {"note"=>51, "timestamp"=>7384.055000002263},
   {"note"=>45, "timestamp"=>7883.249999998952},],


  


  MAPPINGS : left side is midi note, right is timestamp in seconds

  


  {
 48=>234.3489,
 45=>124.334489,
 51=>2789.34,
}


  


  That Events are a sequential array of midi notes and time taken from recordings or standard midi file. The number is in milliseconds but I convert for ffmpeg before feeding the arguments.

  


  The mappings are just in seconds and tell the program what to show when certain midi notes are encountered as we loop through the events and begin slicing the video.

  


  The command I send to ffmpeg is constructed like this :

  


  "ffmpeg -an -y -ss #{begin_at} -i #{project_tempfile_url} -t #{slice_duration} -c:v libx264 #{temp_url}"


  


  When I concatenate these slices, they only look exact when my notes are very consistent like a kickdrum doing 4/4 rythms. Anything too fast or varied creates unpleasant results.

  


  Is there a specific set of commands that will tell ffmpeg to cut down to the frame ? I think keyframe are not an ideal answer but not sure. I also think I can adjust by making sure that I only ever map the notes to keyframes, I can settle for it but it would be great if I could just cut almost anywhere between start and end like ANYWHERE like

  


    rand(0...video.length)
  # and then have
  332.3253613134


  


  But I may just be dreaming :P

  


  Do you think that I would be better off writing a custom c program to cut frames like this ? I understand that frame rates could be an issue and that there may actually not be any data at 7.34667898999 seconds and that it might be here instead : 7.356788722342 and that ffmpeg probably searches for the nearest frame from whatever timestamp you input, but I feel like there must be a way to get good results still despite these limitations.

  


  Thank you so much in advance for those who take the time to read this and understand this issue.

  


• How do I download the image with metadata in Python ? [closed]

  19 octobre 2024, par Temp Account

  I am downloading some images in Python from the Airtable API and am trying to make a slideshow with them using ffmpeg. I download the images :

  


  urllib2.urlretrieve(img['url'], "output/images/image_"+str(i)+".jpeg")


  


  However, when I run the following ffmpeg command

  


  ffmpeg -framerate 4/60 -i output/images/image_%d.jpeg output/out.mp4


  


  I get the following error :

  


  ffmpeg version 6.1.1-3ubuntu5 Copyright (c) 2000-2023 the FFmpeg developers
  built with gcc 13 (Ubuntu 13.2.0-23ubuntu3)
  configuration: --prefix=/usr --extra-version=3ubuntu5 --toolchain=hardened --libdir=/usr/lib/x86_64-linux-gnu --incdir=/usr/include/x86_64-l
inux-gnu --arch=amd64 --enable-gpl --disable-stripping --disable-omx --enable-gnutls --enable-libaom --enable-libass --enable-libbs2b --enable
-libcaca --enable-libcdio --enable-libcodec2 --enable-libdav1d --enable-libflite --enable-libfontconfig --enable-libfreetype --enable-libfribi
di --enable-libglslang --enable-libgme --enable-libgsm --enable-libharfbuzz --enable-libmp3lame --enable-libmysofa --enable-libopenjpeg --enab
le-libopenmpt --enable-libopus --enable-librubberband --enable-libshine --enable-libsnappy --enable-libsoxr --enable-libspeex --enable-libtheo
ra --enable-libtwolame --enable-libvidstab --enable-libvorbis --enable-libvpx --enable-libwebp --enable-libx265 --enable-libxml2 --enable-libx
vid --enable-libzimg --enable-openal --enable-opencl --enable-opengl --disable-sndio --enable-libvpl --disable-libmfx --enable-libdc1394 --ena
ble-libdrm --enable-libiec61883 --enable-chromaprint --enable-frei0r --enable-ladspa --enable-libbluray --enable-libjack --enable-libpulse --enable-librabbitmq --enable-librist --enable-libsrt --enable-libssh --enable-libsvtav1 --enable-libx264 --enable-libzmq --enable-libzvbi --enab
le-lv2 --enable-sdl2 --enable-libplacebo --enable-librav1e --enable-pocketsphinx --enable-librsvg --enable-libjxl --enable-shared
  libavutil      58. 29.100 / 58. 29.100
  libavcodec     60. 31.102 / 60. 31.102
  libavformat    60. 16.100 / 60. 16.100
  libavdevice    60.  3.100 / 60.  3.100
  libavfilter     9. 12.100 /  9. 12.100
  libswscale      7.  5.100 /  7.  5.100
  libswresample   4. 12.100 /  4. 12.100
  libpostproc    57.  3.100 / 57.  3.100
[mjpeg @ 0x593283e5e3c0] bits 150 is invalid
[mjpeg @ 0x593283e5e3c0] bits 28 is invalid
[image2 @ 0x593283e5d380] Could not find codec parameters for stream 0 (Video: mjpeg (Lossless), none(bt470bg/unknown/unknown), lossless): uns
pecified size
Consider increasing the value for the 'analyzeduration' (0) and 'probesize' (5000000) options
Input #0, image2, from 'output/images/image_%d.jpeg':
  Duration: 00:01:00.00, start: 0.000000, bitrate: N/A
  Stream #0:0: Video: mjpeg (Lossless), none(bt470bg/unknown/unknown), lossless, 0.07 fps, 0.07 tbr, 0.07 tbn
File 'output/out.mp4' already exists. Overwrite? [y/N] y
Stream mapping:
  Stream #0:0 -> #0:0 (mjpeg (native) -> h264 (libx264))
Press [q] to stop, [?] for help
[mjpeg @ 0x593283e5f180] mjpeg: unsupported coding type (cf)
[mjpeg @ 0x593283e5f180] mjpeg: unsupported coding type (c8)
[mjpeg @ 0x593283e5f180] bits 150 is invalid
[vist#0:0/mjpeg @ 0x593283e5f000] Error submitting packet to decoder: Invalid data found when processing input
[mjpeg @ 0x593283e5f180] bits 28 is invalid
[vist#0:0/mjpeg @ 0x593283e5f000] Error submitting packet to decoder: Invalid data found when processing input
[mjpeg @ 0x593283e5f180] mjpeg: unsupported coding type (ce)
[mjpeg @ 0x593283e5f180] mjpeg: unsupported coding type (c6)
[mjpeg @ 0x593283e5f180] unable to decode APP fields: Invalid data found when processing input
    Last message repeated 1 times
[vist#0:0/mjpeg @ 0x593283e5f000] Error submitting packet to decoder: Invalid data found when processing input
[mjpeg @ 0x593283e5f180] unable to decode APP fields: Invalid data found when processing input
[mjpeg @ 0x593283e5f180] invalid id 255
[vist#0:0/mjpeg @ 0x593283e5f000] Error submitting packet to decoder: Invalid data found when processing input
Cannot determine format of input stream 0:0 after EOF
Error marking filters as finished
Error while filtering: Invalid data found when processing input
[vist#0:0/mjpeg @ 0x593283e5f000] Decode error rate 1 exceeds maximum 0.666667
[out#0/mp4 @ 0x593283e603c0] Nothing was written into output file, because at least one of its streams received no packets.
frame=    0 fps=0.0 q=0.0 Lsize=       0kB time=N/A bitrate=N/A speed=N/A    
Conversion failed!



  


  However, downloading the images in Chrome then creating the slideshow is successful. The images from Chrome have metadata of the filetype (JPEG), width and height. The images downloaded with Python have no metadata. How do I download that information so that my ffmpeg command will succeed ?

  


  Thanks !