GStreamer-devel

How do get the number of frames in a video file?

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Nick Haddad

How do get the number of frames in a video file?

I want to retrieve the duration of a video file in frames, but can't
figure out the best way to do this.

Calling...

GstFormat fmt = GST_FORMAT_DEFAULT;
gst_element_query_duration( _pipeline, &fm, &numFrames)

...doesn't work. I'm assuming because the pipeline doesn't know about
the "default format" (GST_FORMAT_TIME works fine).

Which element in my pipeline should I query for the number of video
frames? Is this even possible. Currently I am building a pipeline
using decodebin.

Thanks,
-Nick

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Felipe Contreras

Re: How do get the number of frames in a video file?

On Feb 19, 2008 11:48 PM, Nick Haddad <[hidden email]> wrote:

> I want to retrieve the duration of a video file in frames, but can't
> figure out the best way to do this.
>
> Calling...
>
> GstFormat fmt = GST_FORMAT_DEFAULT;
> gst_element_query_duration( _pipeline, &fm, &numFrames)
>
> ...doesn't work. I'm assuming because the pipeline doesn't know about
> the "default format" (GST_FORMAT_TIME works fine).
>
> Which element in my pipeline should I query for the number of video
> frames? Is this even possible. Currently I am building a pipeline
> using decodebin.

Do you need it at any point in time or would it be OK at the end of
the playback?

--
Felipe Contreras

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Wim Taymans

Re: How do get the number of frames in a video file?

In reply to this post by Nick Haddad

On Tue, 2008-02-19 at 16:48 -0500, Nick Haddad wrote:

You could probably get the time duration and then use the framerate to
get the number of frames. This only works if the file has a constant
framerate, of course. A better alternative it to just implement the
DEFAULT query in the relevant elements (quite trivial for avi/qt
demuxers).

Wim

> Thanks,
> -Nick
>
>
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Nick Haddad

Re: How do get the number of frames in a video file?

In reply to this post by Felipe Contreras

I really need to get this information before playback starts. I want
to present the user with the frame count after they open a file.

If there is no generalized way to do do this (by asking the decode
bin?) Is there a way seek through by frames without decoding the video
in the files? If there is then I can do a quick walk through frame by
frame to do my count.

Thanks,
-Nick

On Feb 20, 2008, at 5:54 AM, Felipe Contreras wrote:

> On Feb 19, 2008 11:48 PM, Nick Haddad <[hidden email]> wrote:
>> I want to retrieve the duration of a video file in frames, but can't
>> figure out the best way to do this.
>>
>> Calling...
>>
>> GstFormat fmt = GST_FORMAT_DEFAULT;
>> gst_element_query_duration( _pipeline, &fm, &numFrames)
>>
>> ...doesn't work. I'm assuming because the pipeline doesn't know
>> about
>> the "default format" (GST_FORMAT_TIME works fine).
>>
>> Which element in my pipeline should I query for the number of video
>> frames? Is this even possible. Currently I am building a pipeline
>> using decodebin.
>
> Do you need it at any point in time or would it be OK at the end of
> the playback?
>
> --
> Felipe Contreras

Nick Haddad

Re: How do get the number of frames in a video file?

Anyone else have ideas on how to best do this?

Thanks,
-Nick

On Feb 20, 2008, at 9:53 AM, Nick Haddad wrote:

> I really need to get this information before playback starts. I want
> to present the user with the frame count after they open a file.
>
> If there is no generalized way to do do this (by asking the decode
> bin?) Is there a way seek through by frames without decoding the video
> in the files? If there is then I can do a quick walk through frame by
> frame to do my count.
>
> Thanks,
> -Nick
>
> On Feb 20, 2008, at 5:54 AM, Felipe Contreras wrote:
>
>> On Feb 19, 2008 11:48 PM, Nick Haddad <[hidden email]> wrote:
>>> I want to retrieve the duration of a video file in frames, but can't
>>> figure out the best way to do this.
>>>
>>> Calling...
>>>
>>> GstFormat fmt = GST_FORMAT_DEFAULT;
>>> gst_element_query_duration( _pipeline, &fm, &numFrames)
>>>
>>> ...doesn't work. I'm assuming because the pipeline doesn't know
>>> about
>>> the "default format" (GST_FORMAT_TIME works fine).
>>>
>>> Which element in my pipeline should I query for the number of video
>>> frames? Is this even possible. Currently I am building a pipeline
>>> using decodebin.
>>
>> Do you need it at any point in time or would it be OK at the end of
>> the playback?
>>
>> --
>> Felipe Contreras
>
>
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Wim Taymans

Re: How do get the number of frames in a video file?

On Thu, 2008-02-21 at 09:49 -0500, Nick Haddad wrote:
> Anyone else have ideas on how to best do this?

Go to PAUSED, wait for paused to happen by listening to the ASYNC_DONE
message or by polling or by doing a blocking gst_element_get_state().
Then you can get all the info.

Wim

>
> Thanks,
> -Nick
>
> On Feb 20, 2008, at 9:53 AM, Nick Haddad wrote:
>
> > I really need to get this information before playback starts. I want
> > to present the user with the frame count after they open a file.
> >
> > If there is no generalized way to do do this (by asking the decode
> > bin?) Is there a way seek through by frames without decoding the video
> > in the files? If there is then I can do a quick walk through frame by
> > frame to do my count.
> >
> > Thanks,
> > -Nick
> >
> > On Feb 20, 2008, at 5:54 AM, Felipe Contreras wrote:
> >
> >> On Feb 19, 2008 11:48 PM, Nick Haddad <[hidden email]> wrote:
> >>> I want to retrieve the duration of a video file in frames, but can't
> >>> figure out the best way to do this.
> >>>
> >>> Calling...
> >>>
> >>> GstFormat fmt = GST_FORMAT_DEFAULT;
> >>> gst_element_query_duration( _pipeline, &fm, &numFrames)
> >>>
> >>> ...doesn't work. I'm assuming because the pipeline doesn't know
> >>> about
> >>> the "default format" (GST_FORMAT_TIME works fine).
> >>>
> >>> Which element in my pipeline should I query for the number of video
> >>> frames? Is this even possible. Currently I am building a pipeline
> >>> using decodebin.
> >>
> >> Do you need it at any point in time or would it be OK at the end of
> >> the playback?
> >>
> >> --
> >> Felipe Contreras
> >
> >
> > -------------------------------------------------------------------------
> > This SF.net email is sponsored by: Microsoft
> > Defy all challenges. Microsoft(R) Visual Studio 2008.
> > http://clk.atdmt.com/MRT/go/vse0120000070mrt/direct/01/
> > _______________________________________________
> > gstreamer-devel mailing list
> > [hidden email]
> > https://lists.sourceforge.net/lists/listinfo/gstreamer-devel
>
>
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Nick Haddad

Re: How do get the number of frames in a video file?

I understand how to get the duration in nanonseconds after pausing a
pipeline, that is working fine in my code. But asking for frames is
a little trickier, especially for variable frame rate files, which I
would like to support.

Should I be trying to ask the decodebin for the duration in frames?
Is the file source a better element to ask?

Thanks for your help,
-nick

On Feb 21, 2008, at 9:57 AM, Wim Taymans wrote:

>
> On Thu, 2008-02-21 at 09:49 -0500, Nick Haddad wrote:
>> Anyone else have ideas on how to best do this?
>
> Go to PAUSED, wait for paused to happen by listening to the ASYNC_DONE
> message or by polling or by doing a blocking gst_element_get_state().
> Then you can get all the info.
>
> Wim
>
>>
>> Thanks,
>> -Nick
>>
>> On Feb 20, 2008, at 9:53 AM, Nick Haddad wrote:
>>
>>> I really need to get this information before playback starts. I
>>> want
>>> to present the user with the frame count after they open a file.
>>>
>>> If there is no generalized way to do do this (by asking the decode
>>> bin?) Is there a way seek through by frames without decoding the
>>> video
>>> in the files? If there is then I can do a quick walk through
>>> frame by
>>> frame to do my count.
>>>
>>> Thanks,
>>> -Nick
>>>
>>> On Feb 20, 2008, at 5:54 AM, Felipe Contreras wrote:
>>>
>>>> On Feb 19, 2008 11:48 PM, Nick Haddad <[hidden email]>
>>>> wrote:
>>>>> I want to retrieve the duration of a video file in frames, but
>>>>> can't
>>>>> figure out the best way to do this.
>>>>>
>>>>> Calling...
>>>>>
>>>>> GstFormat fmt = GST_FORMAT_DEFAULT;
>>>>> gst_element_query_duration( _pipeline, &fm, &numFrames)
>>>>>
>>>>> ...doesn't work. I'm assuming because the pipeline doesn't know
>>>>> about
>>>>> the "default format" (GST_FORMAT_TIME works fine).
>>>>>
>>>>> Which element in my pipeline should I query for the number of
>>>>> video
>>>>> frames? Is this even possible. Currently I am building a
>>>>> pipeline
>>>>> using decodebin.
>>>>
>>>> Do you need it at any point in time or would it be OK at the end of
>>>> the playback?
>>>>
>>>> --
>>>> Felipe Contreras
>>>
>>>
>>> -------------------------------------------------------------------------
>>> This SF.net email is sponsored by: Microsoft
>>> Defy all challenges. Microsoft(R) Visual Studio 2008.
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>>> https://lists.sourceforge.net/lists/listinfo/gstreamer-devel
>>
>>
>> -------------------------------------------------------------------------
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>

Jameswalter

Re: How do get the number of frames in a video file?

In reply to this post by Nick Haddad

In order to determine the number of frames in a video file via the API by provided by OpenCV, we need to utilize what are called capture properties, or what OpenCV calls CAP_PROP — anytime you see a constant starting with CAP_PROP_* , you should know it's related to video processing.