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• Best way to go about video playback for WebAssembly, Linux, Windows, and Android

  13 janvier 2021, par Michael Macha

  I'm currently working on a game as a passtime during quarantine. It currently builds, via a Makefile, for WASM, Linux, and Windows ; and is eventually planned to be ported to Android through NDK. The API used is (primarily) SDL, with SDL Image and SDL Mixer, and all graphics go through OpenGL.

  


  As of the moment, all graphics, sound, and control is running perfectly ; but I would like to add video cut scenes and I'm uncertain of how to do this with WASM. I recognize that maybe half of the system resources are available in a browser, and am willing to drop fidelity in the web version to compensate. Currently, all code is in C and GLSL ; but if I need to I can add C++, or a little extra JavaScript.

  


  My compilers, for each platform, are gcc, emcc, and mingw32. They're all called through Maketools. As of the moment, it looks like I can just use FFMPEG for gcc & mingw ; but what's best for emcc, which does not have an FFMPEG port available ? Will I need to call something else, or use some specific browser function ? What is the simplest way to go about this, and does anyone have a basic tutorial for in-browser video with WebAssembly ?

  


  For a little further data, I'm debuting my project on Itch.io. For a launched-in-browser game, they require a zip file with an HTML file called index.html, and any support files, within it. (Total file size is effectively limited to 1 GB.) I'm expecting a minimum of 640x480 resolution, but would prefer higher. I'm currently digging through online examples but haven't yet found anything sufficiently basic. (This might change as I keep digging, and I'll update the question if I find anything.)

  


• Create drawbox with ffmpeg between specific seconds (without reencoding whole video - faster)

  31 mars 2022, par protter

  My plan was to put a transparent red box behind a video. This box should only be present from second 1-45.
But if the videos are 3 hours long, the process takes a long time although it only has to process 45 seconds.

  


  My first attempt takes too long :

  


  ffmpeg -i %1 -vf drawbox=0:9*ih/10:iw:ih/10:t=fill:color=red@0.5:enable='between(t,1,45)' "%~dp0transpred\%~n1%~x1

  


  Then i tried splitting the video into two parts. put the box on the first video, and then put the two back together again.

  


  ffmpeg  -ss 00:00:00.0000 -i %1 -to 00:00:45.0000  -vf drawbox=0:9*ih/10:iw:ih/10:t=fill:color=red@0.5:enable='between(t,1,45)' "%~dp0transpred\%~n1A%~x1"

  


  FFMpeg -ss 00:00:45.0000 -i %1 -c:v copy -c:a copy -avoid_negative_ts make_zero "%~dp0transpred\%~n1B%~x1"

  


  But i don't even have to try to put these two together, because they are not separated exactly at the second. I have read that this is due to "timestamps" and the different video and audio streams.

  


  Now I'm trying an approach to create a stream with the bar, and then overlay it with the finished video. I haven't quite managed that yet, and I don't know if it's faster.
Shortening the video is very fast.

  


  EDIT (Added as a replacement for the comment later)

  


  Thanks for your help I have almost done it with a slightly different approach. Unfortunately, the second part now always has no sound. No matter if I put A and B (B no sound) or B and A (A no sound) together.

  


  

  1. First split with mkvmerge so i have no worrys about the keyframes and get the exact time
mkvmerge --split timestamps:00:00:45.100 A.MKV -o splitmkm.mkv

  


  2. Then add the Bar (Black because of easier testing) :
ffmpeg -i splitmkm-001.mkv -vf drawbox=0:9*ih/10:iw:ih/10:t=fill BAR1.MKV

  


  3. Merge (mkvmerge ends with error) :
ffmpeg -safe 0 -f concat -i list.txt -c copy output1.mkv

  


  


  EDIT (Answer to kesh)

  


  This was the error Again, audio codec config's must match across all your concat files. The drawbox changed the audio Codec from AC-3 to Vorbis.

  


  the procedure is now :

  


  

  1. mkvtoolnix\mkvmerge --split timestamps:00:00:05.100  %1 -o A_splitmkm.mkv with mkvmerge i have an exact split at the time, and i don't have to learn about keyframes.

  


  2. ffmpeg -i A_splitmkm-001.mkv -vf drawbox=0:9*ih/10:iw:ih/10:t=fill:color=red A_BARmkm.MKV create the Bar

  


  3. ffmpeg -i A_BARmkm.MKV -i A_splitmkm-001.mkv -map 0:v  -map 1 -map -1:v  -c copy A_BARwithAudio.mkv redo the step with the changed audio from drawbox

  


  4. ffmpeg -safe 0 -f concat -i list.txt -map 0  -c copy A_output1.mkv merge

  


  


  Now everything works.
Thanks alot !

  


• ffmpeg make image and movie in one command

  22 juin 2012, par knishua

  this is the situation :
  given a thumbnail, i need to overlay it on top of an image.

  so, i need to scale image pass it as parameter to overlay pass that to drawtext.

  I have got so far, adding multiple text + overlay + thumbnail,

  1. ffmpeg -threads 8 -i D:/imagesequence/background.jpg -vf "movie='D\:/imagesequence/dpx/thumbnail.jpg' [watermark]; [in][watermark] overlay=(main_w-overlay_w)/2:(main_h-overlay_h)/3[water];[water] drawtext=fontsize=32:fontcolor=White:fontfile=/Windows/Fonts/arial.ttf:text='shotName':x=(w)/2:y=(h)-50,drawtext=fontsize=28:fontcolor=White:fontfile=/Windows/Fonts/arial.ttf:text='Notes \:':x=(w)/5:y=(h)-90,drawtext=fontsize=28:fontcolor=White:fontfile=/Windows/Fonts/arial.ttf:text='Frame Range \:':x=(w)/5:y=(h)-130,drawtext=fontsize=28:fontcolor=White:fontfile=/Windows/Fonts/arial.ttf:text='Lens \:':x=(w)/5:y=(h)-170,drawtext=fontsize=28:fontcolor=White:fontfile=/Windows/Fonts/arial.ttf:text='Undistortion \:':x=(w)/5:y=(h)-210,drawtext=fontsize=28:fontcolor=White:fontfile=/Windows/Fonts/arial.ttf:text='Image Sequence \:':x=(w)/5:y=(h)-250,drawtext=fontsize=28:fontcolor=White:fontfile=/Windows/Fonts/arial.ttf:text='Date \:':x=(w)/5:y=(h)-290,drawtext=fontsize=28:fontcolor=White:fontfile=/Windows/Fonts/arial.ttf:text='Element Name \:':x=(w)/5:y=(h)-330,drawtext=fontfile=/Windows/Fonts/arial.ttf:text='FUTUREWORKS':x=130:y=200:fontsize=54:fontcolor=White[out]" D:\imagesequence\dpx\brn_055.0000.dpx

  2. ffmpeg -threads 8 -i D:\imagesequence\dpx\brn_055.%04d.dpx -vf "drawtext=fontfile=/Windows/Fonts/arial.ttf:text='shotcam':x=(w)/2:y=(h)-35:fontsize=24:fontcolor=Yellow,drawtext=fontfile=/Windows/Fonts/arial.ttf:text='Frame \:':x=(w)-600:y=(h)-35:fontsize=24:fontcolor=Yellow,drawtext=fontfile=/Windows/Fonts/arial.ttf:text='Focal Length \:':x=(w)-600:y=(h)-65:fontsize=24:fontcolor=Yellow" D:\imagesequence\dpx\test2.mov

  3. how do i scale an image and pass it to movie, in 1

  4. how do i make a blackscreen size that of an image say
     'D :\imagesequence\dpx\brn_055.0001.dpx' and pass it to input in 1

  5. is it possible do bother 1 and 2 in one command line ( ffmpeg ....)
     i.e. make an image from first point ( 1 ) and continue with making .mov ( of 1 image + input from point 2 )

  or in other words if it is not possible to do (1 + 2) in one command then is it possible to first execute 1 then execute 2 ( but with output from 1)
  do it