cloud engineer
If your audio is out of sync, you can fix using ffmpeg.
ffmpeg -i source.mp4 \ -i livestream.mp4 \ -map 0:0 -map 1:1 \ -acodec copy \ -vcodec copy \ -itsoffset 0.100 \ output.mp4 |
The ffmpeg fix is fast. A 1GB file took less than 30 seconds to run. Adjust -tsoffset until you find the sweet spot.
If you have a video with audio sync issues, you can easily fix it using ffmpeg. It takes 2 inputs: the filename and delay: 0.100 is 100 ms or 0.1 seconds. Output file has -fixed appended to it. It’s fast. Only takes 2-3 seconds to process a 1.5 hour recording.
Here’s the script.
ffmpeg -i livestream.mp4 \ -itsoffset 0.100 \ -i livestream.mp4 \ -map 0:0 -map 1:1 \ -acodec copy \ -vcodec copy \ livestream-fixed.mp4 |
How to convert MP3 to OGG audio format.
ffmpeg -i in.mp3 -ar 48000 -vn -c:a libvorbis out.ogg |
If you have sample rate errors, use -vn.
If you have video files that are formatted in MPEG-2, video files with a .m2ts extension, you can convert them to MP4 using ffmpeg.
ffmpeg -i input.ts -c:v libx264 -c:a aac output.mp4 |
The video is encoded using open format H.264, while audio is encoded using AAC.
This is a follow up to a previous post about FFMPEG. In addition to sending a RTMP stream, you can also set a start time and duration.
Here’s how to set the start time using -ss option and -to for the duration. Video will start at 1 min 23 secs and play until 2 mins.
ffmpeg -ss 00:01:23 -i video.mp4 -to 00:02:00 -c copy -copyts cut.mp4 |
Here’s how to start time to start the video at 1 min 23 sec for RTMP streaming. Please note, the start time option needs to be before the input file.
ffmpeg -ss 00:01:23 \ -re -i $1 -acodec libmp3lame -ar 44100 -b:a 128k \ -pix_fmt yuv420p -profile:v baseline -s 1280x720 -bufsize 6000k \ -vb 1200k -maxrate 1500k -deinterlace -vcodec libx264 \ -preset veryfast -g 30 -r 30 -f flv \ -flvflags no_duration_filesize \ "rtmp://username:password@yourserver:1935/live/backup" |