I am having trouble using the output from PiCamera capture function (directed in a BytesIO stream) and opening it using the PIL library. Here is the code (based on the PiCamera basic examples):
#Camera stuff
camera = PiCamera()
camera.resolution = (640, 480)
stream = io.BytesIO()
sleep(2)
try:
for frame in camera.capture_continuous(stream, format = "jpeg", use_video_port = True):
frame.seek(0)
image = Image.open(frame) //THIS IS WHERE IS CRASHES
#OTHER STUFF THAT IS NON IMPORTANT GOES HERE
frame.truncate(0)
finally:
camera.close()
stream.close()
The error is : PIL.UnidentifiedImageError: cannot identify image file <_io.BytesIO object at 0xaa01cf00>
Any help would be greatly appreciated :)
Have a nice day!
The problem is simple but I am wondering why the io library works that way.
One simply needs to seek back the stream to 0 after truncating it or seek to 0 and then simply call truncate with no parameter (all after you are done opening the image). Like so:
for frame in camera.capture_continuous(stream, format = "jpeg", use_video_port = True):
stream.seek(0)
image = Image.open(stream)
#Do stuff with image
stream.seek(0)
stream.truncate()
Basically when you open the image and do some operation on it, the pointer of the BytesIO can move around and end up somewhere else than the zero position. After that when you call truncate(0) it does not move the pointer back to zero as I thought it would (seems logical to me to move the pointer back to where the truncation occurs). When to code runs once more, the capture writes in the stream but this time it does not start writing at the beginning and everything breaks after that.
Hope this can help someone in the future :)
I'm editing all frames of an existing mp4 video in MATLAB (doing it in a for loop).
After I'm done editing, I want to save the new set of frames to a new output video file, but in mp4 rather than .avi (that seems to be the default).
I thought changing the filename extension is sufficient, but apparently it's not.
Any ideas?
newVid = VideoWriter(outputfilename);
newVid.FrameRate = fps;
newVid.Quality = 100;
open(newVid)
for...
writeVideo(newVid,imgs{i})%within the for loop saving one frame at a time
end
close(newVid)
Renaming the file is not sufficient. You also need to specify the codec you want. In your case, you need to include an additional parameter into the VideoWriter constructor that consists of the codec you want to use as a MATLAB
string. In your case, specify 'MPEG-4':
newVid = VideoWriter(outputfilename, 'MPEG-4'); % New
newVid.FrameRate = fps;
newVid.Quality = 100;
open(newVid);
for ...
% Rest of your code here
BTW, have a look at the documentation in the future. It clearly shows you what to do if you want to save to a new format, and not AVI: https://www.mathworks.com/help/matlab/ref/videowriter.html#input_argument_d0e1094625
You need to pass a profile argument to matlab's videowriter.
From Matlab Help, VideoWriter(filename,profile) creates a VideoWriter object and applies a set of properties tailored to a specific file format (such as 'MPEG-4' or 'Uncompressed AVI').
In your case, you need to pass the string MPEG-4 to the profile argument.
I just received a 30 day trial of the Computer Vision System Toolbox, and I just tested it out. I found this code online that separates video from audio:
file='movie.AVI';
file1='targetfile.wav';
hmfr= video.MultimediaFileReader(file,'AudioOutputPort',true,'VideoOutputPort',false);
hmfw = video.MultimediaFileWriter(file1,'AudioInputPort',true,'FileFormat','WAV');
while ~isDone(hmfr)
audioFrame = step(hmfr);
step(hmfw,audioFrame);
end
close(hmfw);
close(hmfr);
but I can't run it, I only get the error:
Undefined variable "video" or class "video.MultimediaFileReader".
I'm not quite sure what this means, does it refer to my code or the computer vision system toolbox? I checked, I have all the requirements and the add-on manager says it's properly installed, so I'm not quite sure why I get this error.
I think your task is quite easier than you think it is. It can be done without any reliance on toolboxes.
That's how:-
1. Read your video file and get its sample rate using audioread.
2. Then use audiowrite to write it as an audio file.
[input_file, Fs] = audioread('movie.AVI');
audiowrite('target_file.WAV', input_file, Fs);
%If your path is set to default then MATLAB may give you 'Permission Denied' Error.
%Change the path or give different full path like: 'D:\target_file.WAV' while audiowriting
I have a ".mat" file supposedly containing a [30720000x4 double] matrix (values from accelerometers). When I try to open this file with "Import data" in Matlab I get the following error:
Error using load
Can't read file F:\vibration_exp_2\GR_UB50n\bearing1\GR_UB50n_1_2.mat.
Error using load
Unknown text on line number 1 of ASCII file
F:\vibration_exp_2\GR_UB50n\bearing1\GR_UB50n_1_2.mat
"MATLAB".
Error in uiimport/runImportdata (line 456)
datastruct = load('-ascii', fileAbsolutePath);
Error in uiimport/gatherFilePreviewData (line 424)
[datastruct, textDelimiter, headerLines]= runImportdata(fileAbsolutePath,
type);
Error in uiimport (line 240)
[ctorPreviewText, ctorHeaderLines, ctorDelim] = ...
The filesize is 921MB which is the same as my other files that do open. I also tried opening the file using python, but no success. Any suggestions? I use MATLAB R2013b .
More info:
How the file was create:
%% acquisition of vibration data
% input:
% sample rate in Hz (max. 51200 Hz, should be used as bearing
% faults are high-frequent)
% time in seconds, stating the duration of the measurement
% (e.g. 600 seconds = 10 minutes)
% filename for the file to be saved
%
% examples:
% data = DAQ(51200, 600, 'NF1_1.mat');
% data = DAQ(51200, 600, 'NF1_2.mat');
function data = DAQ(samplerate,time,filename)
s = daq.createSession('ni'); % Creates the DAQ session
%%% Add the channels as accelerometer channels (meaning IEPE is turned on)
s.addAnalogInputChannel('cDAQ1Mod1','ai0','Accelerometer');
s.addAnalogInputChannel('cDAQ1Mod1','ai1','Accelerometer');
s.addAnalogInputChannel('cDAQ1Mod1','ai2','Accelerometer');
s.addAnalogInputChannel('cDAQ1Mod1','ai3','Accelerometer');
%s.addAnalogInputChannel('cDAQ1Mod2','ai0','Accelerometer');
s.Rate = samplerate;
s.NumberOfScans = samplerate*time;
%%% Defining the Sensitivities in V/g
s.Channels(1).Sensitivity = 0.09478; %31965, top outer
s.Channels(2).Sensitivity = 0.09531; %31966, back outer
s.Channels(3).Sensitivity = 0.09275; %31964, top inner
s.Channels(4).Sensitivity = 0.09363; %31963, back inner
data = s.startForeground(); %Acquiring the data
save(filename, 'data');
More info:
When I open the file using a simple text editor I can see a lot of characters that do not make sense but also the first line:
MATLAB 5.0 MAT-FILE, Platform: PCWIN64, Created on: Thu Apr 30
16:29:07 2015
More info:
The file itself: https://www.dropbox.com/s/r7mavil79j47xa2/GR_UB50n_1_2.mat?dl=0
It is 921MB.
EDIT:
How can I recover my data?
I've tried this, but got memory errors.
I've also tried this, but it did not work.
I fear I can't add many good news to what you know already, but it hasn't been mentioned yet.
The reason the .mat-file can't be load is due to the data beeing corrupted. What makes it 'unrecoverable' is the way it is stored internally. The exact format is specified in the MAT-File Format Documentation. So I decided to manually construct a simple reader to specifically read your .mat file.
It makes sense, that the splitmat.m can't recover anything, as it will basicly split the data into chunks, one stored variable per chunk, however in this case there is only 1 variable stored and thus only one chunk, which happens to be the corrupted one.
In this case, the data is stored as a miCOMPRESSED, which is a normal matlab array compressed using gzip. (Which, as a side note, doesn't seem like a good fit for 'random' vibration data.) This might explain previous comments about the smaller file size then the full data, as the filesize matches exatly with the internally stored value.
I extracted the compressed archive and tried to uncompress it in a variety of ways. Basicly it is a '.gz' without the header, that can be appended manually. Unfortunatly there seems to be a corrupted block near the start of the dataset. I am by no means an expert on gzip, but as far as I know the dictionary (or decryption key) is stored dynamicly which makes all data useless from the point the block is corrupted. If you are really eager, there seems to be a way to recover data even behind the point where data is corrupted, but that method is massively timeconsuming. Also the only way to validate data of those sections is manual inspection, which in your case might proof very difficult.
Below is the code, that I used to extract the .gz-file, so if you want to give it a try, this might get you started. If you manage to decrypt the data, you can read it as described in the MAT-File Format, 13f.
corrupted_file_id = fopen('corrupt.mat','r');
%% some header data
% can be skipped replacing this block with
% fread(id,132);
%header of .mat file
header_text = char(fread(corrupted_file_id,116,'char')');
subsystem_data_offset = fread(corrupted_file_id,8,'uint8');
version = fread(corrupted_file_id,1,'int16');
endian_indicator = char(fread(corrupted_file_id,2,'int8')');
data_type = fread(corrupted_file_id,4,'uint8');
%data_type is 15, so it is a compressed matlab array
%% save te content
data_size = fread(corrupted_file_id,1,'uint32');
gz_file_id = fopen('compressed_array.gz','w');
% first write a valid gzip head
fwrite(gz_file_id,hex2dec('1f8b080000000000'),'uint64',0,'b');
% then write the data sequentialy
step = 1:1e3:data_size;% 1MB steps
for idx = step
fwrite(gz_file_id,fread(corrupted_file_id,1e3,'uint8'));
end
step = step(end):data_size;% 1B steps
for idx = step
fwrite(gz_file_id,fread(corrupted_file_id,1,'uint8'));
end
fclose(gz_file_id);
fclose(corrupted_file_id);
To answer literally to the question, my suggestion would be to make sure first that the file is okay. This tool on File Exchange apparently knows how to diagnose corrupted .MAT files starting with version V5 (R8):
http://www.mathworks.com/matlabcentral/fileexchange/6893-matcat-mat-file-corruption-analysis-tool
The file's size (indices going out of range) seems to be a problem. Octave, which should read .mat files, gives the error
memory exhausted or requested size too large for range of Octave's index type
To find out what is wrong you may need to write a test program outside MatLab, where you have more control over memory management. Examples are here, including instructions on how to build them on your own platform. These stand-alone programs may not have the same memory issues. The program matdgns.c is specifically made to check .mat files for errors.
I am having a problem when creating an avi file using Matlab. My aim is to use an edge filter on an entire video and save the file as an avi. The filter works fine, my problem is the writing of the avi file.
My code:
vidFile = VideoReader('video.avi');
edgeMov = avifile('edges','fps',30);
for i = 1:vidFile.numberofframes
frameI = read(vidFile,i);
frameIgray = rgb2gray(frameI);
edgeI = edge(frameIgray,'canny',0.6);
edgeIuint8 = im2uint8(edgeI);
edgeIuint8(:,:,2) = edgeIuint8(:,:,1);
edgeIuint8(:,:,3) = edgeIuint8(:,:,1);
edgeMov = addframe(edgeMov,edgeIuint8);
end
edgeMov = close(edgeMov)
When the loop finishes and the avifile is closed, I go to play the video and it says "Windows Media Player encountered a problem while playing this file". I've also tried, without success, Media Player Classic and VLC which lead me to believe that the problem must be the file itself. Using GSpot I checked the file and it said that the AVI header is corrupt.
Retrying the loop again returned exactly the same problem. What's confusing me is when I run the loop for a smaller number of frames, 30 for example, the video writes fine and I can watch it. The size of the video I am trying to convert is in excess of 1000 frames so I don't know if size is a problem?
Any help would be greatly appreciated, thank you.
I've used the following to create AVI
edgeMov = avifile('video.avi','compression','Indeo5','fps',15,'quality',95);
Give it a try.