How to drop first X frames or first X seconds of video
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Hi all,
I have an issue with capturing a single snapshot from one particular device. Very often when starting to stream from one of our capture cards using the decklinksrc element the first few seconds of video are badly tuned/rendered before things finally correct themselves and the video appears normal. The way in which i am taking a screen shot means that the first video frame is output to an image file, which for this device means a very poor snapshot. There is no issue with the v4l2src capture cards as the first frame is always perfectly tuned/rendered. Here is how i am doing it: gst-launch decklinksrc mode=2 connection=4 ! ffmpegcolorspace ! video/x-raw-rgb ! pngenc snapshot=true ! filesink location="frame.png" Is there anyway or any element i can use to drop the first few seconds of video or the first e.g. 90 frames before taking the snapshot? I had read about the valve element and played with it but didn't see how it was going to work (for a start it causes execution to block). Ideally I'd like the command to run and finish with no further interaction as it does at the moment. If there is no real way to do it via a command line, then it would be useful if anyone could point to a way to do it programatically via python. Thanks in advance. _______________________________________________ gstreamer-devel mailing list [hidden email] http://lists.freedesktop.org/mailman/listinfo/gstreamer-devel |
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Hi, Check valve gst element or the probes to check the buffers timestamp to drop or pass the buffer. Best, Angel
2013/6/5 a b <[hidden email]> Hi all, _______________________________________________ gstreamer-devel mailing list [hidden email] http://lists.freedesktop.org/mailman/listinfo/gstreamer-devel |
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Hi Angel,
Thanks for the quick reply! So sounds like these methods are for programming a solution. I had planned to look into the python pygst module in order to get away from relying on executing system calls to gst-launch. Maybe now is the time to do that. Cheers! On Wed, Jun 5, 2013 at 12:52 PM, Angel Martin <[hidden email]> wrote: > Hi, > > Check valve gst element or the probes to check the buffers timestamp to drop > or pass the buffer. > > Best, > > Angel > > 2013/6/5 a b <[hidden email]> >> >> Hi all, >> >> I have an issue with capturing a single snapshot from one particular >> device. >> Very often when starting to stream from one of our capture cards using >> the decklinksrc element the first few seconds of video are badly >> tuned/rendered before things finally correct themselves and the video >> appears normal. >> The way in which i am taking a screen shot means that the first video >> frame is output to an image file, which for this device means a very >> poor snapshot. >> There is no issue with the v4l2src capture cards as the first frame is >> always perfectly tuned/rendered. >> >> Here is how i am doing it: >> >> gst-launch decklinksrc mode=2 connection=4 ! ffmpegcolorspace ! >> video/x-raw-rgb ! pngenc snapshot=true ! filesink location="frame.png" >> >> Is there anyway or any element i can use to drop the first few seconds >> of video or the first e.g. 90 frames before taking the snapshot? >> I had read about the valve element and played with it but didn't see >> how it was going to work (for a start it causes execution to block). >> Ideally I'd like the command to run and finish with no further >> interaction as it does at the moment. >> If there is no real way to do it via a command line, then it would be >> useful if anyone could point to a way to do it programatically via >> python. >> >> Thanks in advance. >> _______________________________________________ >> gstreamer-devel mailing list >> [hidden email] >> http://lists.freedesktop.org/mailman/listinfo/gstreamer-devel > > > > _______________________________________________ > gstreamer-devel mailing list > [hidden email] > http://lists.freedesktop.org/mailman/listinfo/gstreamer-devel > gstreamer-devel mailing list [hidden email] http://lists.freedesktop.org/mailman/listinfo/gstreamer-devel |
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If you prefer the probe method this links could help you:
http://gstreamer.freedesktop.org/data/doc/gstreamer/head/manual/html/chapter-dataaccess.html http://gstreamer.freedesktop.org/data/doc/gstreamer/head/manual/html/section-dynamic-pipelines.html If you prefer a output-selector this one (ossbuild example): http://code.google.com/p/ossbuild/source/browse/trunk/Main/GStreamer/Source/gst-plugins-bad/tests/icles/output-selector-test.c?r=926 2013/6/5 a b <[hidden email]> Hi Angel, _______________________________________________ gstreamer-devel mailing list [hidden email] http://lists.freedesktop.org/mailman/listinfo/gstreamer-devel |
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Thank you very much Angel,
Really appreciate your input on this! On Wed, Jun 5, 2013 at 2:40 PM, Angel Martin <[hidden email]> wrote: > If you prefer the probe method this links could help you: > http://gstreamer.freedesktop.org/data/doc/gstreamer/head/manual/html/chapter-dataaccess.html > http://gstreamer.freedesktop.org/data/doc/gstreamer/head/manual/html/section-dynamic-pipelines.html > > If you prefer a output-selector this one (ossbuild example): > http://code.google.com/p/ossbuild/source/browse/trunk/Main/GStreamer/Source/gst-plugins-bad/tests/icles/output-selector-test.c?r=926 > > > > 2013/6/5 a b <[hidden email]> >> >> Hi Angel, >> >> Thanks for the quick reply! >> So sounds like these methods are for programming a solution. >> I had planned to look into the python pygst module in order to get >> away from relying on executing system calls to gst-launch. Maybe now >> is the time to do that. >> >> Cheers! >> >> >> On Wed, Jun 5, 2013 at 12:52 PM, Angel Martin <[hidden email]> >> wrote: >> > Hi, >> > >> > Check valve gst element or the probes to check the buffers timestamp to >> > drop >> > or pass the buffer. >> > >> > Best, >> > >> > Angel >> > >> > 2013/6/5 a b <[hidden email]> >> >> >> >> Hi all, >> >> >> >> I have an issue with capturing a single snapshot from one particular >> >> device. >> >> Very often when starting to stream from one of our capture cards using >> >> the decklinksrc element the first few seconds of video are badly >> >> tuned/rendered before things finally correct themselves and the video >> >> appears normal. >> >> The way in which i am taking a screen shot means that the first video >> >> frame is output to an image file, which for this device means a very >> >> poor snapshot. >> >> There is no issue with the v4l2src capture cards as the first frame is >> >> always perfectly tuned/rendered. >> >> >> >> Here is how i am doing it: >> >> >> >> gst-launch decklinksrc mode=2 connection=4 ! ffmpegcolorspace ! >> >> video/x-raw-rgb ! pngenc snapshot=true ! filesink location="frame.png" >> >> >> >> Is there anyway or any element i can use to drop the first few seconds >> >> of video or the first e.g. 90 frames before taking the snapshot? >> >> I had read about the valve element and played with it but didn't see >> >> how it was going to work (for a start it causes execution to block). >> >> Ideally I'd like the command to run and finish with no further >> >> interaction as it does at the moment. >> >> If there is no real way to do it via a command line, then it would be >> >> useful if anyone could point to a way to do it programatically via >> >> python. >> >> >> >> Thanks in advance. >> >> _______________________________________________ >> >> gstreamer-devel mailing list >> >> [hidden email] >> >> http://lists.freedesktop.org/mailman/listinfo/gstreamer-devel >> > >> > >> > >> > _______________________________________________ >> > gstreamer-devel mailing list >> > [hidden email] >> > http://lists.freedesktop.org/mailman/listinfo/gstreamer-devel >> > >> _______________________________________________ >> gstreamer-devel mailing list >> [hidden email] >> http://lists.freedesktop.org/mailman/listinfo/gstreamer-devel > > > > _______________________________________________ > gstreamer-devel mailing list > [hidden email] > http://lists.freedesktop.org/mailman/listinfo/gstreamer-devel > gstreamer-devel mailing list [hidden email] http://lists.freedesktop.org/mailman/listinfo/gstreamer-devel |
Re: How to drop first X frames or first X seconds of video
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Yeah, as far as I know, there really isn't a clean way to discard the first n seconds of a source via cli. The best I can think of is to use multifilesink, but that could be really awkward to get working. I'm afraid you'll need to use python.On Wed, Jun 5, 2013 at 10:00 AM, a b <[hidden email]> wrote: Thank you very much Angel, -- Stirling Westrup Programmer, Entrepreneur. https://www.linkedin.com/e/fpf/77228 http://www.linkedin.com/in/swestrup http://technaut.livejournal.com http://sourceforge.net/users/stirlingwestrup _______________________________________________ gstreamer-devel mailing list [hidden email] http://lists.freedesktop.org/mailman/listinfo/gstreamer-devel |
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Hey Stirling,
Yeah, thought so, to be honest, I'm glad in a way as it has forced me to look into the python bindings earlier than planned and already I wish i had done it sooner as it has opened up much more of the richness of gstreamer. Think I'm almost there with a first solution. Thanks all! On Wed, Jun 5, 2013 at 4:38 PM, Stirling Westrup <[hidden email]> wrote: > Yeah, as far as I know, there really isn't a clean way to discard the first > n seconds of a source via cli. The best I can think of is to use > multifilesink, but that could be really awkward to get working. > > I'm afraid you'll need to use python. > > > > On Wed, Jun 5, 2013 at 10:00 AM, a b <[hidden email]> wrote: >> >> Thank you very much Angel, >> >> Really appreciate your input on this! >> >> On Wed, Jun 5, 2013 at 2:40 PM, Angel Martin <[hidden email]> >> wrote: >> > If you prefer the probe method this links could help you: >> > >> > http://gstreamer.freedesktop.org/data/doc/gstreamer/head/manual/html/chapter-dataaccess.html >> > >> > http://gstreamer.freedesktop.org/data/doc/gstreamer/head/manual/html/section-dynamic-pipelines.html >> > >> > If you prefer a output-selector this one (ossbuild example): >> > >> > http://code.google.com/p/ossbuild/source/browse/trunk/Main/GStreamer/Source/gst-plugins-bad/tests/icles/output-selector-test.c?r=926 >> > >> > >> > >> > 2013/6/5 a b <[hidden email]> >> >> >> >> Hi Angel, >> >> >> >> Thanks for the quick reply! >> >> So sounds like these methods are for programming a solution. >> >> I had planned to look into the python pygst module in order to get >> >> away from relying on executing system calls to gst-launch. Maybe now >> >> is the time to do that. >> >> >> >> Cheers! >> >> >> >> >> >> On Wed, Jun 5, 2013 at 12:52 PM, Angel Martin <[hidden email]> >> >> wrote: >> >> > Hi, >> >> > >> >> > Check valve gst element or the probes to check the buffers timestamp >> >> > to >> >> > drop >> >> > or pass the buffer. >> >> > >> >> > Best, >> >> > >> >> > Angel >> >> > >> >> > 2013/6/5 a b <[hidden email]> >> >> >> >> >> >> Hi all, >> >> >> >> >> >> I have an issue with capturing a single snapshot from one particular >> >> >> device. >> >> >> Very often when starting to stream from one of our capture cards >> >> >> using >> >> >> the decklinksrc element the first few seconds of video are badly >> >> >> tuned/rendered before things finally correct themselves and the >> >> >> video >> >> >> appears normal. >> >> >> The way in which i am taking a screen shot means that the first >> >> >> video >> >> >> frame is output to an image file, which for this device means a very >> >> >> poor snapshot. >> >> >> There is no issue with the v4l2src capture cards as the first frame >> >> >> is >> >> >> always perfectly tuned/rendered. >> >> >> >> >> >> Here is how i am doing it: >> >> >> >> >> >> gst-launch decklinksrc mode=2 connection=4 ! ffmpegcolorspace ! >> >> >> video/x-raw-rgb ! pngenc snapshot=true ! filesink >> >> >> location="frame.png" >> >> >> >> >> >> Is there anyway or any element i can use to drop the first few >> >> >> seconds >> >> >> of video or the first e.g. 90 frames before taking the snapshot? >> >> >> I had read about the valve element and played with it but didn't see >> >> >> how it was going to work (for a start it causes execution to block). >> >> >> Ideally I'd like the command to run and finish with no further >> >> >> interaction as it does at the moment. >> >> >> If there is no real way to do it via a command line, then it would >> >> >> be >> >> >> useful if anyone could point to a way to do it programatically via >> >> >> python. >> >> >> >> >> >> Thanks in advance. >> >> >> _______________________________________________ >> >> >> gstreamer-devel mailing list >> >> >> [hidden email] >> >> >> http://lists.freedesktop.org/mailman/listinfo/gstreamer-devel >> >> > >> >> > >> >> > >> >> > _______________________________________________ >> >> > gstreamer-devel mailing list >> >> > [hidden email] >> >> > http://lists.freedesktop.org/mailman/listinfo/gstreamer-devel >> >> > >> >> _______________________________________________ >> >> gstreamer-devel mailing list >> >> [hidden email] >> >> http://lists.freedesktop.org/mailman/listinfo/gstreamer-devel >> > >> > >> > >> > _______________________________________________ >> > gstreamer-devel mailing list >> > [hidden email] >> > http://lists.freedesktop.org/mailman/listinfo/gstreamer-devel >> > >> _______________________________________________ >> gstreamer-devel mailing list >> [hidden email] >> http://lists.freedesktop.org/mailman/listinfo/gstreamer-devel > > > > > -- > Stirling Westrup > Programmer, Entrepreneur. > https://www.linkedin.com/e/fpf/77228 > http://www.linkedin.com/in/swestrup > http://technaut.livejournal.com > http://sourceforge.net/users/stirlingwestrup > > _______________________________________________ > gstreamer-devel mailing list > [hidden email] > http://lists.freedesktop.org/mailman/listinfo/gstreamer-devel > gstreamer-devel mailing list [hidden email] http://lists.freedesktop.org/mailman/listinfo/gstreamer-devel |
Re: How to drop first X frames or first X seconds of video
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Hi OP!
I know this thread is old, but did you manage to solve the issue in an elegant way? Would be great if you could post your solution here. Regards, Alexey |
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