> On 13 Aug 2020, at 2:35 am, Rich Andrews <[email protected]> wrote: > > On Tue, Aug 11, 2020 at 11:54 PM Shaun Procter <[email protected] > <mailto:[email protected]>> > wrote: > >>> On 12 Aug 2020, at 9:01 am, Rich Andrews <[email protected]> >> wrote: >>> >>> Is there any trick to slow down ffmpeg on a simple stream mapping? >>> >>> Stream mapping: >>> Stream #0:0 -> #0:0 (pcm_s16le (native) -> pcm_s16le (native)) >>> >>> Given an input file that is looped and output with a command such as: >>> >>> ffmpeg-4.2.1-armhf-static/ffmpeg -y -t 200 -stream_loop -1 -i >> HoldMusic.wav >>> -map 0:a:0 -f wav output.wav >>> >>> ffmpeg can move the data really quickly! >>> >>> bitrate=1411.2kbits/s speed= 262x >>> >>> Any way to get that speed down to ~1x? My purpose is that ffmpeg is >> being >>> used as a child subprocess and I would like to be able to test its >> behavior >>> in-situ. There is a lot of timing in my application between fork and >> join >>> and having ffmpeg be slow would be really helpful. >>> >>> Push comes to shove, I'll just use another program to more slowly copy, >> but >>> that wouldn't be as good as using ffmpeg itself since it has a host of >>> behaviors as a child process regarding signaling and return codes. Come >> to >>> think of it, since I built ffmpeg, maybe I can just build a variant that >>> sleeps frequently? >>> >> >> You can use the -re flag like this, >> >> ffmpeg-4.2.1-armhf-static/ffmpeg -re -y -t 200 -stream_loop -1 -I >> HoldMusic.wav -map 0:a:0 -f wav output.wav >> >> “The FFmpeg's "-re" flag means to "Read input at native frame rate. Mainly >> used to simulate a grab device." i.e. if you wanted to stream a video file, >> then you would want to use this, otherwise it might stream it too fast (it >> attempts to stream at line speed by default). My guess is you typically >> don't want to use this flag when streaming from a live device, ever.” - >> https://trac.ffmpeg.org/wiki/StreamingGuide >> >> Hope that helps. >> >> Shaun >> >> > I feel silly for having looked at that very switch and didn't bother trying > it thinking that the input file doesn't have a framerate. '-re' works > perfectly. Thank you for the perfect solution!
No worries at all, am glad I could help. It’s definitely not silly and we all need to start somewhere. The main thing is you asked for help and that shows intelligence. > _______________________________________________ > ffmpeg-user mailing list > [email protected] <mailto:[email protected]> > https://ffmpeg.org/mailman/listinfo/ffmpeg-user > <https://ffmpeg.org/mailman/listinfo/ffmpeg-user> > > To unsubscribe, visit link above, or email > [email protected] <mailto:[email protected]> with > subject "unsubscribe". _______________________________________________ ffmpeg-user mailing list [email protected] https://ffmpeg.org/mailman/listinfo/ffmpeg-user To unsubscribe, visit link above, or email [email protected] with subject "unsubscribe".
