Specifically, I'd like to write the Windows Media Player frames, such as theWM/MediaClassPrimaryID, WM/MediaClassSecondaryID and WM/WMCollectionGroupID frames.
I'm using PowerShell, but C# would be good too.
I'm a bit rusty, but the following should be mostly correct. I remember these tags being UTF-16 but you'll probably want to get an existing tag and try decoding its value with the Unicode encoder to be sure.
// Get or create the ID3v2 tag.
TagLib.Id3v2.Tag id3v2_tag = file.GetTag(TagLib.TagTypes.Id3v2, true);
if(id3v2_tag != null) {
// Get the private frame, create if necessary.
PrivateFrame frame = PrivateFrame.Get(id3v2_tag, "WM/MediaClassPrimaryID", true);
// Set the frame data to your value. I am 90% sure that these are encoded with UTF-16.
frame.PrivateData = System.Text.Encoding.Unicode.GetBytes(value);
}
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.
I have 1000th of PDF generated from emails containing .png (I am not owner of the generator). For some reasons, those PDF are very very slow to render with the Imaging system I am using (I am not the developer of that system and may not change it).
If I use iTextSharp and implement a IRenderListener to count the Images to be rendered, there are thousands per page (99% being 1 or 2 pixels only). But if I count the Images in the resources of the PDF, there are only a few (~tens).
I am counting the images in the resources, per page, with the code here after
var dict = pdfReader.GetPageN(currentPage)
PdfDictionary res = (PdfDictionary)PdfReader.GetPdfObject(dict.Get(PdfName.RESOURCES));
PdfDictionary xobj = (PdfDictionary)PdfReader.GetPdfObject(res.Get(PdfName.XOBJECT));
if (xobj != null)
{
foreach (PdfName name in xobj.Keys)
{
PdfObject obj = xobj.Get(name);
if ((obj.IsIndirect()))
{
PdfDictionary tg = (PdfDictionary)PdfReader.GetPdfObject(obj);
PdfName subtype = (PdfName)PdfReader.GetPdfObject(tg.Get(PdfName.SUBTYPE));
if (PdfName.IMAGE.Equals(subtype))
{
Count++
And my IRenderListener looks like this:
class ImageRenderListener : IRenderListener
{
public void RenderImage(iTextSharp.text.pdf.parser.ImageRenderInfo renderInfo)
{
PdfImageObject image = renderInfo.GetImage();
if (image == null) return;
var refObj = renderInfo.GetRef();
if (refObj == null)
Count++; // but why no ref ??
else
Count++;
}
I just started to learn about PDF specification and iTextSharp this evening, to analyze my PDF and understand what could be wrong... if I am correct, I see that many images to be rendered that are not referencing a resource (refObj == null) and that they are .png (image.streamContentType.FileExtension = "png"). So, I think those are the images making the rendering so slow...
For testing purpose, I would like to delete those images from the PDF but don't find how to proceed.
I only found code samples to remove image that are in the resources... but the images I want to delete are not :/
Is there any code sample somewhere to help me ? I did google on "iTextSharp remove object", etc... but there was nothing similar to my case :(
Let me start with the blunt observation that you have a shitty PDF.
The image you see when opening the PDF in a PDF viewer seems to be composed of several small 1- or 2-pixel images. The drawing operations to show these pixels one by one is suboptimal, no matter which imaging system you use: you are faced with a bad PDF.
In your first snippet, I see that you loop over all of the indirect objects stored in the the XObject resources of each page in search of images. You count these images, resulting in a number of Image XObjects stored in the PDF. If you add up all the Count values for all the pages, this number can be higher than the actual number of Image XObject stored in the PDF as you don't take into account that some images can be reused on different pages.
You do not count the inline images that are stored in the content streams. I'm biased. In the ISO committees for PDF, I'm on the side of the group of people saying that "inline images are evil" and "inline images should die". For now, we didn't succeed in getting rid of inline images, but we introduced some substantial limitations that should reduce the (ab)use of inline images in PDF that conform to ISO-32000-2 (the PDF 2.0 spec that is due in 2016).
You've already discovered that your PDF has inline images. Those are the images where refObj == null. They are not stored as indirect objects; they are stored inline, in the content stream of the page. As you can imagine based on my feelings towards inline images, I consider your PDF being a bad PDF for this reason (although it does conform to ISO-32000-1).
The presence of inline images is a first explanation why you have a different image count: when you loop over the indirect objects you only find part of the images. When you parse the document for images, you also find the inline images.
A second explanation could be the fact that the Image XObject are used more than once. That's the whole point of not using inline images. For instance: if you have an image that represents a logo that needs to be repeated on every page, one could use inline images. That would be a bad idea: the same image bytes would be present in the PDF as many times as there are pages. One should use an Image XObject. In this case, the image bytes of the logo are stored only once in an indirect object. There's a reference to this object from every page, so that the image bytes are stored in the document only once. In a 10-page document, you can see 10 identical images on 10 pages, but when looking inside the document, you'll find only one image that is referenced from every page.
If you remove Image XObjects by removing the indirect objects containing the image stream objects, you have to be very careful: are you sure you're not corrupting your document? Because there's a reference to the Image XObject in the content stream of your page. This reference points to an entry in the /XObjects entry of the page's /Resources. This /XObject references to the stream object with the image bytes. If you remove that indirect object without removing the references (e.g. from the content stream), you break your PDF. Some viewers will ignore those errors, but at some point in time some tool (or some body) is going to complain that your PDF is corrupt.
If you want to remove inline images, you have to parse all the content streams in your PDF: page content streams as well as Form XObject content streams. You have to rewrite all these streams and make sure all inline images are removed. That is: all objects that that start with the BI operator (Begin Image) and end with the EI operator (End Image).
That's a task for a PDF specialist who knows both iTextSharp and ISO-32000-1 inside-out. The solution to your problem probably doesn't fit into an answering window on StackOverflow.
I'm the original author of iText. From a certain point of view, iText is like a sharp knife. A sharp knife is a very good tool that can be used for many good things. However, you can also seriously cut your fingers when you're not using the knife in a correct way. I hope you'll be careful and that you're not going to create a whole series of damaged PDF files.
For instance: you assume that some of the files in the PDF are PNGs because iText suggests to store them as PNGs. However: PNG is not supported by ISO-32000-1, so your assumption that your PDF contains PNGs is wrong. I honestly worry when I see questions like yours.
I'm trying to grab a screenshot with renderer.domElement.toDataURL("image/png"), and save it to a file.
The image is the right size, but it's black.
I have preserveDrawingBuffer turned on.
I think I'm decoding and saving the file correctly, because when I hexdump it I can see the correct initial characters for the PNG format, as well as the IHDR and IDAT chunk headers. However the closing IEND is missing.
Any known issues here? Hints? Windows 7/Firefox up to date if it matters.
Thanks... (Sorry if this is dumb, I'm very new to three.js)
I had somewhat similar problems with Windows 7/Firefox. PNG Data URL's would be randomly truncated or something, much shorter than a successful PNG export. Trying to set that data url as image src resulted in "Image corrupt" exception or something in FF. As little sense it makse, setting a small window.setTimeout (10ms) between rendering and getting the data URL helped in my case. Maybe Firefox needs a rest from the JS engine before it refreshes some canvas internal state or something.. weird.
I switched to JPG format (smaller files => truncation less of an issue?) and still saw it not working, then I tried this tip which I found here
If you want to save data that is derived from a Javascript
canvas.toDataURL() function, you have to convert blanks into plusses.
If you do not do that, the decoded data is corrupted:
<?php
$encodedData = str_replace(' ','+',$encodedData);
$decodedData = base64_decode($encodedData);
?>
This worked. Thanks, Mekal.
This tip seems to apply to JPGs only. I saw PNGs decoding correctly without the + replacement, and corruptly with it. I can use JPGs so my personal problem is solved. However I never saw a PNG that wasn't black even when decoded correctly and not truncated.
Kind of a lousy situation either way, I feel like. What is up with the +'s?
A black texture is a sign that you did not indicate the texture needs to be updated.
Also, you do not need to use canvas.toDataURL(). You can pass in the canvas reference to the THREE.Texture object.
var canvas = document.getElementById('#myCanvas');
var texture = new THREE.Texture(canvas);
texture.needsUpdate = true;
// Now render the scene
I'm building an App with actionscript 3.0 in my Flash builder. This is a followup question this question.
I need to upload the bytearray to my server, but the function i use to convert the bitmapdata to a ByteArray is super slow, so slow it freezes up my mobile device. My code is as follows:
var jpgenc:JPEGEncoder = new JPEGEncoder(50);
trace('encode');
//encode the bitmapdata object and keep the encoded ByteArray
var imgByteArray:ByteArray = jpgenc.encode(bitmap);
temp2 = File.applicationStorageDirectory.resolvePath("snapshot.jpg");
var fs:FileStream = new FileStream();
trace('fs');
try{
//open file in write mode
fs.open(temp2,FileMode.WRITE);
//write bytes from the byte array
fs.writeBytes(imgByteArray);
//close the file
fs.close();
}catch(e:Error){
Is there a different way to convert it to a byteArray? Is there a better way?
Try to use blooddy library: http://www.blooddy.by . But i didn't test it on mobile devices. Comment if you will have success.
Use BitmapData.encode(), it's faster by orders of magnitude on mobile http://help.adobe.com/en_US/FlashPlatform/reference/actionscript/3/flash/display/BitmapData.html#encode%28%29
You should try to find a JPEG encoder that is capable of encoding asynchronously. That way the app can still be used while the image is being compressed. I haven't tried any of the libraries, but this one looks promising:
http://segfaultlabs.com/devlogs/alchemy-asynchronous-jpeg-encoding-2
It uses Alchemy, which should make it faster than the JPEGEncoder from as3corelib (which I guess is the one you're using at the moment.)
A native JPEG encoder is ideal, asynchronous would be good, but possibly still slow (just not blocking). Another option:
var pixels:ByteArray = bitmapData.getPixels(bitmapData.rect);
pixels.compress();
I'm not sure of native performance, and performance definitely depends on what kind of images you have.
The answer from Ilya was what did it for me. I downloaded the library and there is an example of how to use it inside. I have been working on getting the CameraUI in flashbuilder to take a picture, encode / compress it, then send it over via a web service to my server (the data was sent as a compressed byte array). I did this:
by.blooddy.crypto.image.JPEGEncoder.encode( bmp, 30 );
Where bmp is my bitmap data. The encode took under 3 seconds and was easily able to fit into my flow of control synchronously. I tried async methods but they ultimately took a really long time and were difficult to track for things like when a user moved from cell service to wifi or from tower to tower while an upload was going on.
Comment here if you need more details.
I'm looking for some sample code to show me how to add metadata to the wav files we create.
Anyone?
One option is to add your own chunk with a unique id. Most WAV players will ignore it.
Another idea would to be use a labl chunk, associated with a que set at the beginning or end of the file. You'd also need a que chunk. See here for a reference
How to write the data is simple
Write "RIFF".
save the file position.
Write 4 bytes of 0's
Write all the existing chunks. Keep count of bytes written.
Add your chunk. Be sure to get the chunksize right. Keep
count of bytes written.
rewind to the saved position. Write the new size (as a 32-bit
number).
Close the file.
It's slightly more complicated if you are adding things to an existing list chunk, but the same principle applies.
Maybe the nist file format will give you what you want:
NIST
Here is a lib that could help, but im afraid it looks old. NIST Lib
Cant find more useful information right now how exactly to use it, and im afraid the information papers from my company must stay there. :L/
Try code below
private void WaveTag()
{
string fileName = "in.wav";
WaveReadWriter wrw = new WaveReadWriter(File.Open(fileName, FileMode.Open, FileAccess.ReadWrite));
//removes INFO tags from audio stream
wrw.WriteInfoTag(null);
//writes INFO tags into audio stream
Dictionary<WaveInfo, string> tag = new Dictionary<WaveInfo, string>();
tag[WaveInfo.Comments] = "Comments...";
wrw.WriteInfoTag(tag);
wrw.Close();
//reads INFO tags from audio stream
WaveReader wr = new WaveReader(File.OpenRead(fileName));
Dictionary<WaveInfo, string> dir = wr.ReadInfoTag();
wr.Close();
if (dir.Count > 0)
{
foreach (string val in dir.Values)
{
Console.WriteLine(val);
}
}
}
from http://alvas.net/alvas.audio,articles.aspx#id3-tags-for-wave-files
If you examine the wave file spec you'll see that there does not seem to be room for annotations of any kind. An option would be to wrap the wave file with your own format that includes custom information but you would in effect be creating a whole new format that would not be readable by users who do not have your app. But you might be ok with that.