[FFmpeg-user] Growing file processing

[Moritz Barsnick]

On Sat, Mar 02, 2019 at 11:02:03 +0100, Bouke / VideoToolShed wrote:
> Next, it is dog slow, sorta kinda defeating the whole idea.

I thought the whole point was that the "receiving" ffmpeg was too fast,
in relation to the processing "speed" of the sending ffmpeg. And that
the "receiving" side needed a chance not to exit on EOF.

The tail "pipe" shouldn't slow anything down, except that there's the
disk R/W I/O involved.

There could be a minor issue in "tail" processing in text mode,
buffered line by line. You will find references online to a "bintail",
but I am otherwise at a loss of tools which can ignore EOF. Named pipes
as am alternative probably also transfer EOF.

> (Since the data is piped at a speed that FFmpeg will never be able to
> catch up with the original…)

Huh? Gregor wrote:
> 2 - Growing file generation slower than processing
> ffmpeg.exe -i input.mxf growing.mkv
> ffmpeg.exe -i growing.mkv -c copy output.mkv
> > ffmpeg stops when it reaches the current end of the growing file.                                                                                                                 

So Bouke, what's to catch up? Did you misread the original poster's
request?

> bouke$ ffmpeg -i /Users/bouke/Desktop/Judith/Harding.mxf  -an -s 120x40 -t 15  -y  /Users/bouke/Desktop/Judith/test.mp4

You may have overlooked that /Users/bouke/Desktop/Judith/Harding.mxf is
being created at a slower speed, and not an existing finalized file.


> Stream #0:0 -> #0:0 (mpeg2video (native) -> mpeg4 (native))
> Press [q] to stop, [?] for help
> frame=  375 fps=136 q=2.0 Lsize=     365kB time=00:00:15.00 bitrate= 199.6kbits/s    
> video:363kB audio:0kB subtitle:0kB other streams:0kB global headers:0kB muxing overhead: 0.674411%
> 
> vs
> bouke$ tail -c +1 -F /Users/bouke/Desktop/Judith/Harding.mxf  | ffmpeg -i - -an -s 120x40 -t 15  -y  /Users/bouke/Desktop/Judith/test.mp4
>   Stream #0:0 -> #0:0 (mpeg2video (native) -> mpeg4 (native))
> frame=  375 fps= 28 q=2.0 Lsize=     365kB time=00:00:15.00 bitrate= 199.5kbits/s dup=1 drop=0    
> video:363kB audio:0kB subtitle:0kB other streams:0kB global headers:0kB muxing overhead: 0.674757%

28 vs 136 fps is certainly peculiar.

Moritz