[MEncoder-users] grabbing a single frame

[Steven Miller]

Thank you both for your responses. The video does show something I would expect to see in an individual frame.

I will take a look at using mencoder and ffmeg to try to grab a single frame.

I'll let you know how I make out.



-- Sent from my Palm Pixi
On Mar 24, 2011 5:52 PM, Peter <pscientist at inbox.com> wrote: 

I'm sure there is some way to see this information, because I've seen it by 

accident. For example, look at the beginning of this youtube video:

<http://www.youtube.com/watch?v=mzJmTCYmo9g>

As the presenter is saying "and they're about to perform..." you can see the 

differential image based on "mid grey" instead of the previous I-frame. His 

clothes get filled in as he moves his hands, and the rest of the image which is 

not moving, remains grey.



Perhaps either MEncoder or FFmpeg could be persuaded to output this information 

if you specify a number of frames or an exact start/stop time, and make it use 

the 'copy' codec? I haven't tried this.



-- 

Peter



On 2011-03-24 4:46 PM, Stjepan Brbot wrote:

> P and B frames contain motion vectors for reconstructing (compensation)

> of current picture from vectors and previous I/P frame blocks plus

> differential DCT coeficients for adding to correct what motion vectors

> were not able to predict. So how to grab such a data and how to present

> it is your question.

>

> In many book about video coding it is shown an example with current and

> next full video image and what you get when subtract them showing

> temporal redundancy that is coded. Probably you'd like to see that!

>

> I don't know how to do that but I'd like to get this "differential"

> image too. I think it's done with Matlab's simulink functions.

>

> On Wed, 2011-03-23 at 19:44 -0400, Steven Miller wrote:

>> Is it possible to grab and save a single frame, be it an I or P or B frame?

>> I want the single frame. Not what the decoder would show you. I'm trying to

>> get a feel for how each frame type looks.  I'm using mencoder/libx264.

>>

>> Let me know if I haven't described what I'm after well enough.

>>

>> thanks,

>> Steve

>> _______________________________________________

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>> MEncoder-users at mplayerhq.hu

>> https://lists.mplayerhq.hu/mailman/listinfo/mencoder-users

>

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>





-- 

Peter



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