It's easy to spot a free box in a .mp4 (or ISO BMFF) file. I'm wondering the reason for this box. Is it some sort of padding for file size? Sometimes, I even spotted two consecutive free boxes!
The following is a partial info by mp4dump
[ftyp] size=8+20
major_brand = iso5
minor_version = 0
compatible_brand = avc1
compatible_brand = iso5
compatible_brand = dash
[free] size=8+17
[moov] size=8+637
[mvhd] size=12+108, version=1
timescale = 24000
duration = 14315000
duration(ms) = 596458
There are actually padding boxes, so that other sections can be correctly aligned (it is also ease updates).
Related
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.
Title basically explains it, but I can't for the life of me get away from the A4 page size and I am having to resize each file individually. I have a LOT of files. Nearly 2000 now, and its kinda getting old.
Thank you to anyone who helps in advance!
sheet.paper_size_code = 1
is what you want.
example:
book = Workbook()
sheet = book.add_sheet('2013')
sheet.paper_size_code = 1
sales_units(OUTPUT, header_list, DATE, book, sheet)
book.save('Projections.xls')
I finally got some sort of pdf scanner to work. It reads into the callback functions without a problem, but when I try to NSLog the result from a CGPDFScannerPopString I get a result like this:
ˆ ˛˝ # ˜˜˜ #˜' ˜˜˜ "˜ '˜˜ " ' ˜˜
No string to be found here...
Any ideas of what it can be?
This is my callback function:
static void op_Tj (CGPDFScannerRef s, void *info)
{
CGPDFStringRef string;
if (!CGPDFScannerPopString(s, &string))
return;
NSLog(#"string: %#", (__bridge NSString *)CGPDFStringCopyTextString(string));
}
Thanks already!
Edit: Example PDF
You should be aware that the CGPDFStringRef is not a ASCII string or something similar at all. Cf. http://developer.apple.com/library/mac/documentation/graphicsimaging/Reference/CGPDFString/Reference/reference.html --- it is a "series of bytes—unsigned integer values in the range 0 to 255" which have to be interpreted according to the latest PDF reference.
The PDF reference in turn will tell you that the interpretation of the bytes depends on the font used, and while ASCII-like interpretations are common in case of European languages, they are not mandatory, and in case of Asian languages where font subset embedding is very common, the interpretation may look random.
CGPDFStringCopyTextString tries to interpret those bytes accordingly, but there does not have to be a sensible interpretation as a regular string.
EDIT Inspection of the sample PDF Ron supplied showed that in case of this sample indeed the encoding of the font in object 3 0 (which is dominant on most pages of the document) is not a standard encoding but instead:
<</Type/Encoding
/Differences[0/.notdef/C/O/V/E/R/space/slash/H/L/F/underscore/W/B/five/eight/four
/zero/two/six/D/one/period/three/Z/I/N/G/U/S/T/colon/seven/A/M/P/Y
/plus/nine/X/hyphen/i/s/p/a/t/c/h/n/f/o/K/greater/equal/l/m/y/J/Q
/parenleft/parenright/comma/dollar/ampersand/d/r/v/b/e/u/w/k/g/x/bar
/quotesingle/asterisk/q/question/percent]
>>
Looking at the top of the first document page
COVER / HLF_CWEB_58408485 / 58408485 / 26DEC12 10.30.22Z
BRIEFING INCLUDES FOLLOWING FLIGHTS:
26DEC12 OR0337 EHAM0630 MUVR1710 PHOYE VSM+2/8 179
NEXT FLIGHTS OF AIRCRAFT:
26DEC12 OR0338 MUVR1830 MMUN1940 PHOYE VSM+2/8 213
26DEC12 OR0338 MMUN2105 EHAM0655 PHOYE GPT+2/7 263
27DEC12 OR0365 EHAM0900 TNCB1930 PHOYE BAH+1/8 272
27DEC12 OR0366 TNCB2030 TNCC2110 PHOYE BAH+1/8 250
27DEC12 OR0366 TNCC2250 EHAM0835 PHOYE ASD+1/8 199
that encoding seems to have been created by dealing out the next number starting from one for the next required glyph. This obviously results in a highly individualistic encoding...
That being said the font object does include both an /Encoding entry and a /ToUnicode entry. Thus, if the method CGPDFStringCopyTextString was given a reference to the font here and really tried, it would easily be able to correctly translate those bytes into the corresponding text. That it doesn't achieve anything decent, seems to indicate that it simply does not have the information which font to interpret the bytes for --- I don't assume it doesn't try...
For accurate text extraction, therefore, you have to interpret the bytes in the CGPDFStringRef yourself using the information of the the font in the content stream. If you don't want to do that from scratch, you might be interested in PDFKitten, a framework for extracting data from PDFs in iOS. While it is not yet perfect (some font structures can baffle it), it is a good starting point.
I looked at the man pages, searched here, googled, etc.
Does anyone know the default size used by logrotate?
What reference can you cite stating the default size?
I know I can set size specifically in my config files.
There isn't a default size, because it's an optional flag. logrotate will rotate based on certain criteria that you give it, e.g., file size or time period (daily, weekly, etc). So it's not that it has a default file size (except maybe something like size 0), it's just not a precondition for a file being rotated.
So far as I know, there is no default size for logrotate, no need to waste time on this，set the value yourself in config file.
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.