Verstuurd vanaf mijn iPhone
> Op 12 mei 2015 om 11:31 heeft Werner Robitza <[email protected]> het > volgende geschreven: > >> 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. Would you be so kind to explain why to NOT use the crf option? > _______________________________________________ > ffmpeg-user mailing list > [email protected] > http://ffmpeg.org/mailman/listinfo/ffmpeg-user _______________________________________________ ffmpeg-user mailing list [email protected] http://ffmpeg.org/mailman/listinfo/ffmpeg-user
