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• Video playing, how to play a video back a a rapid rate at random timestamp locations

  10 avril 2020, par Zarc Rowden

  Note : this is a mildly general question that is looking more for pointers in the right direction and not exactly requiring a concise coded answer. I appreciate any and all input, thank you for lending your brain power to me for this moment :)

  



  I have a script that receives midi messages in real time and triggers playback of a single video on various timestamps that are changed/selected regularly and randomly by a user. Currently this is working in the browser, however, I've realized that there is some noticeable latency between (i'm guessing the cause here so please correct me) the moment a request to play a video at a specific time is made(note : the video is not being requested over the wire, this action does not take place until a JS Blob Url is loaded into the player) and the moment where that request is fulfilled and delivered from storage to pixels on the screen.

  



  My question is : Is it reasonable to assume that there is a tool out there, that given the correct video format and optimizations both in the code and in the file that could load an entire, say : 1 gb video into memory and play it back at random timestamps every 60 milliseconds at completely random, constantly changing timestamps.

  



  If you're now all the way down here... Thanks for reading this far, or scanning ! Please let me know if this question makes any sense / could be improved, I'm happy to clarify further.

  


• FFMPEG reports invalid video resolution, video headers container seem to be different from actual frames !

  20 décembre 2011, par Emiliano

  Quick question, i have a movie, which was cut and rendered with Sony Vegas from its original format to a .wmv file. Here comes the tricky part, movie when played, either with VLC or WMP, has a resolution of 656x480 ... BUT when i run a ffmpeg -i on it, it says it has a resolution of 600x480 ....

  I took the time of actually capturing a frame and croping it with photoshop and its 656 and not 600 like ffmpeg its reporting, why would this could be happening ? How could i fix the headers resolution ? Would that have any impact on video re-rendering ? As i said, VLC and WMP seems not to care about the incorrect headers and are playing it right, BUT, jwplayer seems to be using the header information, which i don't blame him, its correct to do that, but why the video headers could be wrong ?

  ffmpeg -i trailer.wmv

  Input #0, asf, from 'trailer.wmv' :
  Duration : 00:01:04.93, start : 3.000000, bitrate : 2144 kb/s
  Stream #0.0 : Audio : wmav2, 44100 Hz, mono, 32 kb/s
  Stream #0.1 : Video : wmv3, yuv420p, 600x480 [PAR 59:54 DAR 295:216], 2065 kb/
  s, 25.00 tb(r)

  And yeah, the PAR/DAR parameters are also wrong, but honestly, i don't understand that technical shit, usually watch video and make sure it look good, any feedback would be appreciated :P

  Is there a way to change the container information with ffmpeg so applications that actually do use the container information don't render video incorrectly ?

• How to reduce the file size during conversion of video from any video to mp4 using ffmpeg &mp4box in PHPmotion ?

  3 juillet 2017, par Balaji Kandasamy

  I am using ffmpeg & mp4box in my PHPmotion site to convert videos to mp4 format. When I convert a 50MB video to mp4, the file size remain same. So Its affecting the video streaming in my site. So I want to reduce the file size of the video in conversion. This is my code example, that I’ve used the site for converting m4v videos in PHPmotion.

  $ffmpeg_cmd2_2 = "$config[path_to_ffmpeg] -i $raw_video_path -vcodec libx264 -vpre veryfast -crf 15 -b 5120000 -threads 0 -acodec libfaac -ac 2 -ab 128k -ar 44100 -f mp4 $new_flv_1";
  
  $mp4box_cmd = "$mp4box_path -add $new_flv_1 $new_flv_2" 

  When I use this command,it converts the m4v file to mp4 format, but the filesize doesn’t change. What command I should use in this to reduce the filesize during video conversion in PHPmotion ? Can anyone write a ffmpeg command to reduce the filesize during conversion ?