Using my Windows 7 64bit machine, I'm trying to generate an avi file from Matlab using the sequence
aviobj = avifile('test.avi', 'fps', 25);
% a loop of aviobj = addframe(aviobj, frame)
close(aviobj)
However, the file generated is corrupt - with VLC it looks sheared and with bad colors, with Media Player it was a black screen, and with Divx Plus player it looks okay but generates a warning.
I've tried specifying other codec types (via avifile('test.avi', 'fps', 25, 'compression', 'TYPE') but Matlab never seems to be able to find that codec - I've tried Indeo and cvid and MSVC and MRLE and many more, but Matlab just generates a "not a supported compression method" warning, and then outright fails when addframe is invoked.
How can I solve the above problem, or alternatively, is there a different, simple way to just generate an avi by adding a frame at a time?
How to generate a video from matlab without codec errors?
try to use mmwrite
http://www.mathworks.com/matlabcentral/fileexchange/15881-mmwrite
Well after a few more searches online and experimentation, looks like others have encountered this problem as well, and suggested just using a different program to compress it and that should also fix the file, so that's what I did:
Generated an uncompressed file
Opened it in VirtualDub(good open-source video software which doesn't require installation)
From the video menu I chose "compression" and selected the "Microsoft Video 1" option
Saved the file via the save-as menu option
It now looks correct in all the players I've tried, and the file is smaller in size.
What you are describing what happens in VLC is probably related to having a resolution that is not supported by the codec. Try resolutions that are multiples of 2,4,8,16 and see what works. VirtualDub probably takes care of that somehow.
Otherwise it's really simple. All you have to do:
aviobj = avifile('example.avi', 'compression', 'none', 'fps', 25);
for i=1:1000
%generating the filenames
filename = strcat(FolderName,'/frame', sprintf('%05d', i),'.bmp');
I = imread(filename);
aviobj = addframe(aviobj,I);
end;
aviobj = close(aviobj);
I know I am replying to a very old thread, but I helped my brother with this and learned a few things that might help others:
My brother had a very small video, the result of an MRI scan, 51x51 pixels. Using VideoWriter with profile "Uncompressed AVI" worked, but did not play well in VLC. Virtualdub also threw errors.
What fixed it, is making sure that the video dimensions where a multiple of 2.
A 96x96 video played fine and could also be transcoded to XVID in virtualdub.
Also, with very small videos, set the video output mode to wingdi in VLC. With OpenGL or Direct3D and overlay mode, the GPU will do the scaling and interpolate pixels in between.
Related
I need to get an mpeg4 file to use in another application, from an original mpeg4 video I loaded into matlab and edited (frame by frame).
To do so, I tried using VideoWriter, setting the quality to 100%:
newVid = VideoWriter(outputfilename, 'MPEG-4');
newVid.FrameRate = fps;
newVid.Quality = 100;
However, the result I'm getting is very poor and if the original unedited video size was ~50MB, the one I get post-edit in matlab is around ~20MB, and I don't know how to keep the quality and size as they were.
I also tried saving as .avi and converting to mpeg4 with ffmpeg, but it gave even poorer results.
Any ideas?
MPEG-4is a compressed format so there is information loss when you save it in this format. Quality is the quality of the compression but you do not want any compression. To force Matlab not to use compression my guess is to use the statement below as the default is H.264
newVid.VideoCompressionMethod = 'none'
I've already made a function to cut out the image, and the part I cut out has a black background. I'm trying to make the black part transparent, then I can generate an image sequence that I can create a video with. I've tried converting the image to a double and then replacing the 0 values with NaN:
J = imread('imgExample.jpg');
J2 = im2double(J);
J2(J2 == 0) = NaN;
imwrite(J2, 'newImg.jpg');
but when I convert it into a video, it doesn't seem to stay. Is there any way to get the black part of the image to be transparent?
From clarifications in comments, you are trying to create a video format that supports alpha transparency using matlab.
In general this seems impossible using matlab alone (at least in matlab 2013 which is the version I use). If you'd like to check if the newest matlab supports videos with alpha transparency, type doc videowriter and have a look at the available formats. If you see anything with transparency options there, take it from there. But the most I see on mine is 24bit RGB videos (i.e. three channels, no transparency).
So matlab does not have the ability to produce native .avi video with alpha transparency.
However, note that this is a very rare video format anyway, and even if you did manage to produce such a video, you would still have to find a suitable viewer which supports playing videos with transparency!
It's therefore important for you to tell us your particular use-case because it may be you're actually trying to do something much simpler (which may or may not be solvable via matlab) (i.e. a case of the XY Problem
E.g. you may be trying to create a video with transparency for the web instead, like here https://developers.google.com/web/updates/2013/07/Alpha-transparency-in-Chrome-video
If this is the case, then I would recommend you attempting the method outlined there; you can create individual .png "frames" with transparency in matlab using the imwrite function. have a look at its documentation, particularly the section about png images and the 'Alpha' property. But beyond that, you'd need an external tool to combine them into a .webm file, since matlab doesn't seem to have a tool like that (at least none that I can see at a glance; there might be a 3rd-party toolkit if you look on the web).
Hope this helps.
I want to read an AVI File in Matlab. I tried it according to this link: http://inside.mines.edu/~whoff/courses/EENG512/lectures/other/Matlab_movies.pdf :
clear all
close all
movieObj = VideoReader('ap001_BL0_SP2_cam03_compressed.avi'); % open file
get(movieObj) % display all information about movie
nFrames = movieObj.NumberOfFrames; %shows 310 in my case
for iFrame=1:2:nFrames
I = read(movieObj,iFrame); % get one RGB image
imshow(I,[]); % Display image
end
I get the following error:
Error using VideoReader/read (line 145) The frame index requested is
beyond the end of the file.
Error in test_video_read (line 9) I = read(movieObj,iFrame); % get
one RGB image
(Shortened) Output from "get(movieObj)" is:
General Settings:
Duration = 10.3333
Name = ap001_BL0_SP2_cam03_compressed.avi
Type = VideoReader
Video Settings:
BitsPerPixel = 24
FrameRate = 30
Height = 1280
NumberOfFrames = 310
VideoFormat = RGB24
Width = 960
So it should be possible to read the first frame, as there are 310 available!
I can play the AVI file in VLC-Player, so the codec should be already installed, right?
I'm using MATLAB R2013a, Windows 7. Can anyone please help, thank you!
VLC player is built using the ffmpeg codecs. VideoReader uses DirectShow and Media Foundation API's that are Windows Platform API's and are different from ffmpeg. So, if a file plays using VLC, it is not guaranteed to be opened by VideoReader. Couple of things you can do:
Can the file be viewed on Windows Media Player? If so, in most cases it should work with VideoReader. If not, then you do not have the suitable codecs. Try installing ffsdhow or K-lite codec pack.
If file works on Windows Media Player but VideoReader does not support, it would indicate a bug. A workaround that has worked for me in the past is that I install codecs mentioned above and give it a try again.
If (1) and (2) do not help, use software like handbrake or Mirro to transcode the file into MP4 which works win VideoReader.
Hope this helps.
Dinesh
I have tested your Matlab code using some avi files and I have no problem with them. So, I think it is your avi file that is causing the error.
I have a similar problem before, where my (mp4) movies can be played in any media players but matlab cannot open them. In my case, the problem is the pixel format when the mp4 movies were compiled (by ffmpeg). By default, my movies were compiled with the High 4:4:4 Predictive (yuv444p) format but Matlab cannot handle this. When I switched to an older pixel format (yuv420p), I don't have any problem loading the movies into Matlab.
You can check if this is the problem using ffprobe, which is part of ffmpeg and you can download them from https://www.ffmpeg.org.
Otherwise, have you tried with an uncompressed avi?
I have a simple code to show an image in Matlab. I use imread() to read it and imshow() to show it. the code it below, and the result in not shown properly. hope someone can help me.
img = imread('/home/samuelpedro/Desktop/API - Projecto/coimbra_aerea.jpg');
figure, imshow(img);
the resulting image is below.
also, if i choose to save it to file as a new jpg it is saved correctly.
UPDATE 1:
weirdly if i choose to show the axes in the preferences>image processing, it is corrected
Locking at your screen-shot, the x- and y-ticks are missing. They should appear in a standard-configuration of Matlab. Maybe something is just messed up in the Matlab-configuration. Try to do this with a clean new ~/.matlab folder (rename the old one before).
Alternatively ... again judging by your screen-shot, this looks like Ubuntu/Unity in the background. Unity needs acceleration (OpenGL), which can be randomly buggy for some Linux graphics drivers. You may want to try to launch matlab in a "clean" X-server (maybe the twm environment) to rule this out.
Save the image as an (uncompressed) bitmap (bmp) and read it with imread. If the jpg is messed up by the imread-routine, this should rule this out.
Last but not least, broken copy of your jpg on your disk, some flipped bits. Run md5sums on your file's copies.
I want to save a MATLAB figure as PDF, with quality 300 DPI, and centered.
So far I managed to save it, but the image appears cropped. I changed the page type to A3 and kind of solves the problem, but I am looking for something more elegant. I am doing it from the GUI, but maybe from the command line is easier in MATLAB.
Is there any package or script that makes this (fundamental task for publications and papers) a bit easier?
Try using the following command:
print -painters -dpdf -r300 test.pdf
You will, of course, already have to have a file named test.pdf in the current directory.
Some notes on the -commands as well.
-painters: this specifies the use of the painters alogrithm for the exporting.
-dpdf: specifies a vector image, specially a pdf in this case. This is through Ghostscript.
-r300: specifies a 300 dpi resolution. -r400 would be 400 dpi and so on.
On an off note. I tend to just save the figure as a high DPI tiff image and import that tiff into another program where I actually assemble my figure(s) for the paper. I tend to lean towards CorelDraw personally.
I would recommend to check the exportfig package
exportfig(gcf, path_to_file, 'format','pdf','Resolution', 300 )
also, you can check fig package, which is nice to call before the exportfig:
figure
plot(x,y)
fig
exportfig(gcf, path_to_file, 'format','pdf','Resolution', 300 )