digitalmars.D.learn - Using ffmpeg in command line with D
Karabuta <Karabutaworld gmail.com> writes:
Hi all, I'm trying to convert an array of video filenames to another format using spawnProcess() from std.process. I want to convert all files in sequence with the command "ffmpeg -i filename.mp4 -o outputfile.webm" where process will be run one process after the other. I am new to this kind of multimedia stuff and all this is currently theoretical. Will this work and is it the right approach used by video convertor front-ends?
Mar 21 2016
Adam D. Ruppe <destructionator gmail.com> writes:
On Monday, 21 March 2016 at 17:26:09 UTC, Karabuta wrote:I am new to this kind of multimedia stuff and all this is currently theoretical. Will this work and is it the right approach used by video convertor front-ends?Eh, it is how I did it before, it works and is pretty easy to do.
Mar 21 2016
cy <dlang verge.info.tm> writes:
On Monday, 21 March 2016 at 17:26:09 UTC, Karabuta wrote:Will this workYes.and is it the right approach used by video convertor front-ends?Well, yes, provisionally. When you invoke "ffmpeg" via spawnProcess, that isolates ffmpeg as its own process, obviously. From a security and maintenance standpoint, that is very, very good. None of the code in ffmpeg has to be considered when writing your own code, other than how it acts when you call it. If ffmpeg scrambles its own memory, your program won't get messed up. If your program scrambles its own memory, ffmpeg won't get corrupted, and neither will your video file. There are a few downsides though. It's expensive to set up that very restricted, isolated interface (executing a process) but considering the amount of number crunching involved in processing videos it's a pretty negligible cost. If you're doing some sort of web server that serves up a million generated pages a minute though, all that executing can bog it down. But you wouldn't use ffmpeg for that. The extreme isolation of a separate process means that you're restricted in what you can do with the video. You can do anything that ffmpeg devs write in their interface, but that's it. If they change the format of their command, all your stuff will break until you fix that, but considering how old ffmpeg is, that's probably not going to happen any time soon. In some cases, there are resources that cannot be reused between two processes, that are very expensive to set up and tear down. You wouldn't use mpv like ffmpeg for instance, because it would have to recreate the video display window every execution. Instead, mpv has a "socket" interface that you can connect to after launching one process, and use that to control the player. So, for video conversion, yes it's the right approach. Your mileage may vary if you want to display that video, or generate videos on-demand from a high performance webserver. (in which case the video processing will still be 99.999% of what slows you down, not process execution).
Mar 22 2016