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• How to stream an image during specific seconds with ffmpeg ?

  14 juillet 2021, par Alex Rypun

  I need to stream an image to RTMP destination for 20 seconds.
I use AWS medialive + mediapackage for streaming.
I'm trying to do it using different framerates (-r) by command :

  


  ffmpeg -loop 1 -r 30 -t 20 -i ./stream_stub.jpg -vcodec libx264 -f flv rtmp://mystream


  


  but the real stream time is from 8 to 14 seconds (depending on framerate).

  


  If I create a video file the duration is 20 seconds (as expected) regardless of framerate :

  


  ffmpeg -loop 1 -r 30 -t 20 -i ./stream_stub.jpg -vcodec libx264 -f flv out.mp4


  


  But for live streaming, I can't reach the expected behavior.

  


  What I'm doing wrong ? And what framerate should I use for a single still image (as I understand 1 fps should be ok) ?

  


• Converting portion of an MP4 to MP3 with FFMpeg with timestamp

  17 juillet 2019, par john

  I can convert portions of an mp3 to and mp3 or and mp4 to an mp4 using FFMpeg with the -ss and -to flags. For example :

  ffmpeg -i sample1.mp4 -ss 00:00:10 -to 00:00:18 -c copy output output.mp4

  or

  ffmpeg -i sample1.mp3 -ss 00:00:14 -to 00:00:27 -c copy output output.mp3

  These work as expected. But when I do this :

  ffmpeg -i sample1.mp4 -ss 00:00:22 -to 00:00:53 -c copy output.mp3

  I get this error :

  Could not write header for output file #0(incorrect codec parameters ?):Invalid argument

  I looked on the FFMpeg site and other sites to see what the missing codec was. if I convert the mp4 to mp3 without the -ss and -to flags the conversion works as expected. Is there another flag I am missing, or do I need to convert from mp4 to mp3 then grab a subsection of the mp3 based on the timestamps ?

  Thanks

• Parsing avconv/ffmpeg rawvideo output ?

  23 avril 2013, par DigitalMan

  I'm about to begin a project that will involve working with the output of avconv/ffmpeg, pixel-by-pixel, in rgb32 format. I intend to work with a raw byte stream, such as from the pipe protocol. Basic pointer arithmetic (C/C++) will be used to iterate over these pixels, and modify them in arbitrary manners in real-time.

  I've created a very small file using rawvideo format and codec, and opened it up in a hex editor. As expected, it's just a series of pixels, read right to left, top to bottom. No distinguishing between lines - no problem, if you know how wide the video is beforehand. No distinguishing between frames - no problem, if you also know how tall the video is. No file header for frame rate, or even what the encoding (rgb32, rgb24, yuv, etc.) is - again, as long as you already know, it can be worked with.

  The problem occurs when - for one reason or another - some bytes are missing. Maybe the stream isn't being examined from the beginning, which is likely be the case in my project, or maybe something just got lost. All the pre-existing knowledge in the world (besides maybe a byte count of what's been missed, not gonna happen) won't prevent it from happily chugging along, with an incorrect offset of line and frame.

  So, what I'm looking for is an option for rawvideo, or possibly some other format/codec, that will allow me to work with the resulting stream at the pixel level, in RGB, yet still have a clear definition of where a new frame begins, even if it happens to start "looking" in the middle of a frame. (Width, height, and framerate will indeed be known.)