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• How to write frames to a video file ?

  23 décembre 2013, par Mike Chen

  I am currently writing an application that read frames from camera, modify them, and save them into a video file. I'm planing to do it with ffmpeg. There's rarely a documentation about ffmpeg. I can't find a way. Does any know how to do it ?

  I need it to be done on unix, and in C or C++. Does any can provide some instructions ?

  Thanks.

  EDIT :

  Sorry, I haven't write clearly. I want some developer APIs to write frames to a video file. I open up camera stream, I get every single frame, then I save them into a video file with those APIs available in ffmpeg's public apis. So using command line tool actually doesn't help me. And I've seen output_example.c under the ffmpeg src folder. It's pretty great that I may copy some parts of the code directly without change. And I am still looking for a easier way.

  Also, I'm thinking of porting my app to iPhone, as far as I know, only ffmpeg has been ported on iPhone. GStreamer is based on glib, and it's all GNU stuff. I'm not sure if I can get it work on iPhone. So ffmpeg is still the best choice for now.

  Any comments is appreciated.

• FFMPEG scaling, how to set scale so width AND height don't exceed a certain amount ?

  12 octobre 2013, par Darius

  I have 2 videos, one is 500 pixels by 100 pixels (just an example, like something recorded sideways on an iphone). And a 1980 x 400 pixels videos. I need the video to convert maintaining aspect ratios. I know of the -vf scale filter such as -vf scale=-1:320, but that only takes the width and scales the height accordingly. My 500 x 100 video would be 320px wide and 1600 pixels tall. That's bad, I need it to be max 500 pixels tall and max width of 320 (just example sizes).

  How would I configure the -vf scale function to do that ?

  Using latest ffmpeg 0.11

  Recap : scale any video to max 500 height : 320 width while keeping aspect ratio

• FFmpeg mp4 videos load very slow outside of network

  6 juin 2014, par user3550401

  I used ffmpeg to convert my videos to mp4 using libx264 and qt fast start. Im playing my videos through the HTML tag, and when im inside my network where my website is, everything plays fast. But when i try to play the video from an outside network, I have to wait about 10 seconds before a 5 second video is played. And even when its playing, its super choppy. Any reason on why this is ? I am playing the videos in Safari on my iPhone.

  Here is how im encoding my videos :

  ffmpeg -i video.ts -i css/watermark.png -filter_complex overlay=10:main_h-overlay_h-10 -shortest -b:v 800k -vcodec libx264 -acodec libfaac -ar 44100 -ac 2 -b:a 128k -movflags faststart -map_metadata -1 video.mp4