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
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 _______________________________________________ MEncoder-users mailing list MEncoder-users@mplayerhq.hu https://lists.mplayerhq.hu/mailman/listinfo/mencoder-users
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 _______________________________________________ MEncoder-users mailing list MEncoder-users@mplayerhq.hu https://lists.mplayerhq.hu/mailman/listinfo/mencoder-users
_______________________________________________ MEncoder-users mailing list MEncoder-users@mplayerhq.hu https://lists.mplayerhq.hu/mailman/listinfo/mencoder-users
-- Peter ____________________________________________________________ Share photos & screenshots in seconds... TRY FREE IM TOOLPACK at http://www.imtoolpack.com/default.aspx?rc=if1 Works in all emails, instant messengers, blogs, forums and social networks.
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@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 >> _______________________________________________ >> MEncoder-users mailing list >> MEncoder-users@mplayerhq.hu >> https://lists.mplayerhq.hu/mailman/listinfo/mencoder-users > > _______________________________________________ > MEncoder-users mailing list > MEncoder-users@mplayerhq.hu > https://lists.mplayerhq.hu/mailman/listinfo/mencoder-users > > -- Peter ____________________________________________________________ Share photos & screenshots in seconds... TRY FREE IM TOOLPACK at http://www.imtoolpack.com/default.aspx?rc=if1 Works in all emails, instant messengers, blogs, forums and social networks. _______________________________________________ MEncoder-users mailing list MEncoder-users@mplayerhq.hu https://lists.mplayerhq.hu/mailman/listinfo/mencoder-users
participants (3)
-
Peter -
Steven Miller -
Stjepan Brbot