[FFmpeg-user] live stream - get data from multimedia filter continuously
ffmpeg at gyani.pro
Mon May 13 07:49:19 EEST 2019
On 13-05-2019 12:36 AM, Thomas Seilund wrote:
> On 12/05/2019 19.25, Gyan wrote:
>> On 12-05-2019 10:43 PM, Thomas Seilund wrote:
>>> Hi All
>>> I capture video stream from webcam and show video on screen.
>>> The same stream goes through the 'metadata' multimedia filter as
>>> shown below:
>>> ffmpeg -y -f v4l2 -input_format mjpeg -s hd480 -r 30 -i /dev/video2
>>> -map '[X]' -pix_fmt yuv420p -f xv Title
>>> The text file 'movement.txt' gets information about each frame. BUT
>>> data is written to text file 'movement.txt' buffered. Is there any
>>> way to write data to text file 'movement.txt' as each frame is
>> Not at present. The file protocol will buffer up to 256 kB and then
>> write out. There is an option to write immediately but it isn't
>> applied to the metadata filter as its I/O context is isolated. I plan
>> to patch that soon-ish.
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> Thanks Gyan.
> Is there another way to get the metadata, ie. lavfi.scene_score, as
> the frame is processed?
> Basically, I want to take some action when there is motion in the video!
If you increase the log level to debug or higher, you should see lines
of the form
[Parsed_select_0 @ 00000000006feb80] n:1524.000000 pts:780288.000000
t:60.960000 key:0 interlace_type:P pict_type:B scene:0.000987 ->
The "scene:" value is what you want.
To capture this, you either redirect stderr to a file or add -report to
your command. The latter will generate a text file in PWD.
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