getting data format info
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Hi,
we are using (or is that abusing?) gstreamer in order to capture video data from an USB camera. For this we have setup a v4lsrc and a fake sink and grab the data in the handoff hook of the latter. So far, so good. However, despite several hours of tinkering we haven't found out how to determine what format (width, height, encoding) the data comes in. What do we need to do to get these values? TIA, Schobi ------------------------------------------------------------------------- This SF.Net email is sponsored by the Moblin Your Move Developer's challenge Build the coolest Linux based applications with Moblin SDK & win great prizes Grand prize is a trip for two to an Open Source event anywhere in the world http://moblin-contest.org/redirect.php?banner_id=100&url=/ _______________________________________________ gstreamer-devel mailing list [hidden email] https://lists.sourceforge.net/lists/listinfo/gstreamer-devel |
Re: getting data format info
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On Mon, Sep 1, 2008 at 11:18 AM, Hendrik Schober <[hidden email]> wrote: Hi, Check the 'caps' in the source pad of the v4lsrc element.
-- Thiago Sousa Santos Embedded Systems and Pervasive Computing Lab (Embedded) Center of Electrical Engineering and Informatics (CEEI) Federal University of Campina Grande (UFCG) ------------------------------------------------------------------------- This SF.Net email is sponsored by the Moblin Your Move Developer's challenge Build the coolest Linux based applications with Moblin SDK & win great prizes Grand prize is a trip for two to an Open Source event anywhere in the world http://moblin-contest.org/redirect.php?banner_id=100&url=/ _______________________________________________ gstreamer-devel mailing list [hidden email] https://lists.sourceforge.net/lists/listinfo/gstreamer-devel |
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In reply to this post by Hendrik Schober
Hendrik Schober wrote:
> Hi, > > we are using (or is that abusing?) gstreamer in order to capture > video data from an USB camera. For this we have setup a v4lsrc > and a fake sink and grab the data in the handoff hook of the > latter. So far, so good. However, despite several hours of > tinkering we haven't found out how to determine what format > (width, height, encoding) the data comes in. > What do we need to do to get these values? > > if you're using gst-laucnh to do that, you can add -v to your command line -- Benoit Fouet Purple Labs S.A. www.purplelabs.com ------------------------------------------------------------------------- This SF.Net email is sponsored by the Moblin Your Move Developer's challenge Build the coolest Linux based applications with Moblin SDK & win great prizes Grand prize is a trip for two to an Open Source event anywhere in the world http://moblin-contest.org/redirect.php?banner_id=100&url=/ _______________________________________________ gstreamer-devel mailing list [hidden email] https://lists.sourceforge.net/lists/listinfo/gstreamer-devel |
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In reply to this post by Thiago Sousa Santos-2
thiagoss wrote:
> > On Mon, Sep 1, 2008 at 11:18 AM, Hendrik Schober <[hidden email] > <mailto:[hidden email]>> wrote: > > Hi, > > we are using (or is that abusing?) gstreamer in order to capture > video data from an USB camera. For this we have setup a v4lsrc > and a fake sink and grab the data in the handoff hook of the > latter. So far, so good. However, despite several hours of > tinkering we haven't found out how to determine what format > (width, height, encoding) the data comes in. > What do we need to do to get these values? > > > Check the 'caps' in the source pad of the v4lsrc element. Thanks for your answer. In fact, we already did that -- and got back a rather long list of caps. But that doesn't tell us which one's currently used. (Also, they specify a range for width and height, while we need the ones that actually are negotiated.) Schobi ------------------------------------------------------------------------- This SF.Net email is sponsored by the Moblin Your Move Developer's challenge Build the coolest Linux based applications with Moblin SDK & win great prizes Grand prize is a trip for two to an Open Source event anywhere in the world http://moblin-contest.org/redirect.php?banner_id=100&url=/ _______________________________________________ gstreamer-devel mailing list [hidden email] https://lists.sourceforge.net/lists/listinfo/gstreamer-devel |
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In reply to this post by Benoit Fouet
Benoit Fouet wrote:
> Hendrik Schober wrote: >> Hi, >> >> we are using (or is that abusing?) gstreamer in order to capture >> video data from an USB camera. For this we have setup a v4lsrc >> and a fake sink and grab the data in the handoff hook of the >> latter. So far, so good. However, despite several hours of >> tinkering we haven't found out how to determine what format >> (width, height, encoding) the data comes in. >> What do we need to do to get these values? >> >> > > if you're using gst-laucnh to do that, you can add -v to your command line No, we're doing this in code (C++). Schobi ------------------------------------------------------------------------- This SF.Net email is sponsored by the Moblin Your Move Developer's challenge Build the coolest Linux based applications with Moblin SDK & win great prizes Grand prize is a trip for two to an Open Source event anywhere in the world http://moblin-contest.org/redirect.php?banner_id=100&url=/ _______________________________________________ gstreamer-devel mailing list [hidden email] https://lists.sourceforge.net/lists/listinfo/gstreamer-devel |
Re: getting data format info
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In reply to this post by Hendrik Schober
On Mon, Sep 1, 2008 at 11:56 AM, Hendrik Schober <[hidden email]> wrote: thiagoss wrote: You should check the caps in the buffers you get from the handoff buffers instead.
-- Thiago Sousa Santos Embedded Systems and Pervasive Computing Lab (Embedded) Center of Electrical Engineering and Informatics (CEEI) Federal University of Campina Grande (UFCG) ------------------------------------------------------------------------- This SF.Net email is sponsored by the Moblin Your Move Developer's challenge Build the coolest Linux based applications with Moblin SDK & win great prizes Grand prize is a trip for two to an Open Source event anywhere in the world http://moblin-contest.org/redirect.php?banner_id=100&url=/ _______________________________________________ gstreamer-devel mailing list [hidden email] https://lists.sourceforge.net/lists/listinfo/gstreamer-devel |
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thiagoss wrote:
> > > On Mon, Sep 1, 2008 at 11:56 AM, Hendrik Schober <[hidden email] > <mailto:[hidden email]>> wrote: > > thiagoss wrote: > > > > On Mon, Sep 1, 2008 at 11:18 AM, Hendrik Schober <[hidden email] > <mailto:[hidden email]> > > <mailto:[hidden email] <mailto:[hidden email]>>> wrote: > > > > Hi, > > > > we are using (or is that abusing?) gstreamer in order to capture > > video data from an USB camera. For this we have setup a v4lsrc > > and a fake sink and grab the data in the handoff hook of the > > latter. So far, so good. However, despite several hours of > > tinkering we haven't found out how to determine what format > > (width, height, encoding) the data comes in. > > What do we need to do to get these values? > > > > > > Check the 'caps' in the source pad of the v4lsrc element. > > Thanks for your answer. > In fact, we already did that -- and got back a rather long > list of caps. But that doesn't tell us which one's currently > used. (Also, they specify a range for width and height, while > we need the ones that actually are negotiated.) > > > You should check the caps in the buffers you get from the handoff > buffers instead. Thanks, we hadn't even found those yet. However, this now leads to another question: Since these are rather suboptimal for us, we need to change them. We could use the ffmpegcolorspace conversion plugin, but IIUC we need to make this and the fakesink use the right pad. Where and how would we do this? When we setup the pipeline? By forcing some caps/pad onto the fakesink's source? Schobi ------------------------------------------------------------------------- This SF.Net email is sponsored by the Moblin Your Move Developer's challenge Build the coolest Linux based applications with Moblin SDK & win great prizes Grand prize is a trip for two to an Open Source event anywhere in the world http://moblin-contest.org/redirect.php?banner_id=100&url=/ _______________________________________________ gstreamer-devel mailing list [hidden email] https://lists.sourceforge.net/lists/listinfo/gstreamer-devel |
Re: getting data format info
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On Mon, Sep 1, 2008 at 12:59 PM, Hendrik Schober <[hidden email]> wrote:
You can do like this: v4lsrc ! ffmpegcolorspace ! capsfilter caps="yourdesiredcaps" ! fakesink If you need scaling put a videoscale between ffmpegcolorspace and capsfilter.
-- Thiago Sousa Santos Embedded Systems and Pervasive Computing Lab (Embedded) Center of Electrical Engineering and Informatics (CEEI) Federal University of Campina Grande (UFCG) ------------------------------------------------------------------------- This SF.Net email is sponsored by the Moblin Your Move Developer's challenge Build the coolest Linux based applications with Moblin SDK & win great prizes Grand prize is a trip for two to an Open Source event anywhere in the world http://moblin-contest.org/redirect.php?banner_id=100&url=/ _______________________________________________ gstreamer-devel mailing list [hidden email] https://lists.sourceforge.net/lists/listinfo/gstreamer-devel |
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thiagoss wrote:
> On Mon, Sep 1, 2008 at 12:59 PM, Hendrik Schober <[hidden email] > <mailto:[hidden email]>> wrote: > > thiagoss wrote: > > > > > > On Mon, Sep 1, 2008 at 11:56 AM, Hendrik Schober <[hidden email] > <mailto:[hidden email]> > > <mailto:[hidden email] <mailto:[hidden email]>>> wrote: > > > > thiagoss wrote: > > > > > > On Mon, Sep 1, 2008 at 11:18 AM, Hendrik Schober > <[hidden email] <mailto:[hidden email]> > > <mailto:[hidden email] <mailto:[hidden email]>> > > > <mailto:[hidden email] <mailto:[hidden email]> > <mailto:[hidden email] <mailto:[hidden email]>>>> wrote: > > > > > > Hi, > > > > > > we are using (or is that abusing?) gstreamer in order > to capture > > > video data from an USB camera. For this we have setup > a v4lsrc > > > and a fake sink and grab the data in the handoff hook > of the > > > latter. So far, so good. However, despite several hours of > > > tinkering we haven't found out how to determine what > format > > > (width, height, encoding) the data comes in. > > > What do we need to do to get these values? > > > > > > > > > Check the 'caps' in the source pad of the v4lsrc element. > > > > Thanks for your answer. > > In fact, we already did that -- and got back a rather long > > list of caps. But that doesn't tell us which one's currently > > used. (Also, they specify a range for width and height, while > > we need the ones that actually are negotiated.) > > > > > > You should check the caps in the buffers you get from the handoff > > buffers instead. > > Thanks, we hadn't even found those yet. > However, this now leads to another question: > Since these are rather suboptimal for us, we need to change > them. We could use the ffmpegcolorspace conversion plugin, > but IIUC we need to make this and the fakesink use the right > pad. > Where and how would we do this? When we setup the pipeline? > By forcing some caps/pad onto the fakesink's source? > > > You can do like this: > > v4lsrc ! ffmpegcolorspace ! capsfilter caps="yourdesiredcaps" ! fakesink > > If you need scaling put a videoscale between ffmpegcolorspace and > capsfilter. That did the trick! We got it working now. Thank you for your support. Schobi ------------------------------------------------------------------------- This SF.Net email is sponsored by the Moblin Your Move Developer's challenge Build the coolest Linux based applications with Moblin SDK & win great prizes Grand prize is a trip for two to an Open Source event anywhere in the world http://moblin-contest.org/redirect.php?banner_id=100&url=/ _______________________________________________ gstreamer-devel mailing list [hidden email] https://lists.sourceforge.net/lists/listinfo/gstreamer-devel |
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