On Tue, May 12, 2015 at 1:25 AM, Joel Lopez <[email protected]> wrote: > Can I add a few lower versions to the mix and a higher one?
Yes, you should do that. > Can I realign the keyframes of the existing files? That's going to be hard. You're better off re-encoding from scratch with a fixed interval. > I'm not so sure how crucial aligned key frames are. What have you seen out > there? The recommendation is definitely to keep them aligned; otherwise you'll run into sync issues. > What bitrates and dimensions do you think they're using? What do you > recommend is good for adaptive bit rate switching? See https://developer.apple.com/library/ios/technotes/tn2224/_index.html#//apple_ref/doc/uid/DTS40009745-CH1-SETTINGSFILES It's a good starting point. > He said I didn't need to change the dimensions when making > different bit rate versions. What's your opinion? Typically you should vary both bit rate and resolution, and frame rate if you're targeting really crappy devices. Changing just the bit rate but not the resolution may make the video look worse at lower bit rates than if it had a lower resolution and the same low bit rate. I recently did a test with bitrate-only switching and I'm not sure if I'd recommend that. > How do I change this command to make the different bitrate or sizes? > > ffmpeg [rawvideo demuxer options if required] -i input -c:v libx264 > -crf 23 -preset medium -pix_fmt yuv420p -c:a libfdk_aac -vbr 5 > -movflags +faststart output.mp4 Check the H.264 encoding guide (https://trac.ffmpeg.org/wiki/Encode/H.264). Do not use the CRF option but use "-b:v 1M" for 1 MBit/s, or similar. Ideally, do a two-pass encode for better quality, if you have the time. _______________________________________________ ffmpeg-user mailing list [email protected] http://ffmpeg.org/mailman/listinfo/ffmpeg-user
