I've probably spent the last 2 weeks searching through Apple Quicktime documentation to resolve what seems like a pretty basic question, but to no avail. Here's the issue...
I've got several short QTMovie files each containing three tracks -- the usual two containing the sound and video, plus an extra video track holding subtitled text images (making two video tracks in all). If I select one of these tracks in Quicktime Pro and export it as an 'Movie To Image Sequence' I might find say, 142 stills spread throughout the duration of the movie. My search method also reports the correct total number of frames.
Now, I've learned that you can take single-frame images, add them to a QTMovie, and set their individual on-screen display times for however long you want using 'attributeForKey:QTMovieDurationAttribute'. But how on earth do I go about accessing that data again? (which essentially just seems like the reverse of this process).
In pseudo-code what I'm trying to do is something like:
{
select video track #2 ...
call up the first image in the sequence ...
access and note its on-screen duration setting ...
call up the second image ...
access and note its duration ...
... repeat until done.
}
I'm not after editing this data or anything -- just finding out how I can get access to individual frames in a video track ... and where the HECK this timing info is hiding inside the bowels of QT.
As a senior citizen I think I'm starting to get too old for this sort of thing and Quicktime is a big, often complex and confusing framework, so if anyone can help me out with some advice or (ideally) just a few lines of sample code here I'd really appreciate it. Thanks in advance :-)
Okay. After several more days of digging and experimentation I finally found the answer to my own question. To get the (next) subtitle image I used:
// access the subtitle track
Track theTrack = [self getVideoSubtitleTrack];
// set flags to find NEXT image (ignoring the current one)...
myFlags = nextTimeStep;
// ... and search forward from current position.
GetTrackNextInterestingTime(theTrack, myFlags, playheadPos, fixed1, &nextInterestingTime, NULL);
This only finds the start of an image object though, and iterating through the track finds the leading edge of each successive image. But I wanted the end time of the current text too.
After getting the start time, I experimented with the seven available flags and found that setting the flag to 'nextTimeTrackEdit' gets the end time.
Related
How are we supposed to implement the environment's render method in gym, so that Monitor's produced videos are not black (as they appear to me right now)? Or, alternatively, in which circumstances would those videos be black?
To give more context, I was trying to use the gym's wrapper Monitor. This wrapper writes (every once in a while, how often exactly?) to a folder some .json files and an .mp4 file, which I suppose represents the trajectory followed by the agent (which trajectory exactly?). How is this .mp4 file generated? I suppose it's generated from what is returned by the render method. In my specific case, I am using a simple custom environment (i.e. a very simple grid world/maze), where I return a NumPy array that represents my environment's current state (or observation). However, the produced .mp4 files are black, while the array clearly is not black (because I am also printing it with matplotlib's imshow). So, maybe Monitor doesn't produce those videos from the render method's return value. So, how exactly does Monitor produce those videos?
(In general, how should we implement render, so that we can produce nice animations of our environments? Of course, the answer to this question depends also on the type of environment, but I would like to have some guidance)
This might not be an exhaustive answer, but here's how I did.
First I added rgb_array to the render.modes list in the metadata dictionary at the beginning of the class.
If you don't have such a thing, add the dictionary, like this:
class myEnv(gym.Env):
""" blah blah blah """
metadata = {'render.modes': ['human', 'rgb_array'], 'video.frames_per_second': 2 }
...
You can change the desired framerate of course, I don't know if every framerate will work though.
Then I changed my render method. According to the input parameter mode, if it is rgb_array it returns a three dimensional numpy array, that is just a 'numpyed' PIL.Image() (np.asarray(im), with im being a PIL.Image()).
If mode is human, just print the image or do something to show your environment in the way you like it.
As an example, my code is
def render(self, mode='human', close=False):
# Render the environment to the screen
im = <obtain image from env>
if mode == 'human':
plt.imshow(np.asarray(im))
plt.axis('off')
elif mode == 'rgb_array':
return np.asarray(im)
So basically return an rgb matrix.
Looking at the gym source code, it seems there are other ways that work, but I'm not an expert in video rendering so for those other way I can't help.
Regarding your question "how often exactly [are the videos saved]?", I can point you to this link that helped me for that.
As a final side note, video saving with a gym Monitor wrapper does not work for a mis-indentation (as of today 30/12/20, gym version 0.18.0), if you want to solve it do like this guy did.
(I'm sorry if my English sometimes felt weird, feel free to harshly correct me)
I am writing an app in which I have two UITextFields...
Starting Text
Destination Text
Now once I place values and hit the search or whatever function I want to call, I Want to reuse these values. The app should record and save these values as cache. And should show them when typing or upon a button click. Is that possible to show them just like Dictionary words show up or Which is more preferable tableView or PickerView? If there is any other please let me know.
Definitely use a UITableView. A UIPicherView is used modally most of the time and not for optional suggestions.
Table view is used in Safari, and a lots of other apps:
As for how to cache the data, you have lots of options. It also depends on how much data you expect.
One easy way would be to simply use NSArray. You can very easily write an NSArray to disk in a plist file and read it back when you need it.
Or you could use Core Data, if you expect lots of data and still want high performance. It will be a lot more difficult though to get used to that API if you've never tried it before. Basically you'll need a simple model with one entity called something like SearchEntry that has a single property text. Then you keep adding new instances to your managed object context and can easily filter the existing values.
Consider the following, I have paragraph data being sent to a view which needs to be placed over a background image, which has at the top and the bottom, fixed elements (fig1)
Fig1.
My thought was to split this into 4 labels (Fig1.example2) my question here is how I can get the text to flow through labels 1 - 4 given that label 1,2 & 3 ar of fixed height. I assumed here that label 3 should be populated prior to 4 hence the layout in the attached diagram.
Can someone suggest the best way of doing this with maybe an example?
Thanks
Wish I could help more, but I think I can at least point you in the right direction.
First, your idea seems very possible, but would involve lots of calculations of text size that would be ugly and might not produce ideal results. The way I see it working is a binary search of testing portions of your string with sizeWithFont: until you can get the best guess for what the label will fit into that size and still look "right". Then you have to actually break up the string and track it in pieces... just seems wrong.
In iOS 6 (unfortunately doesn't apply to you right now but I'll post it as a potential benefit to others), you could probably use one UILabel and an NSAttributed string. There would be a couple of options to go with here, (I haven't done it so I'm not sure which would be the best) but it seems that if you could format the page with html, you can initialize the attributed string that way.
From the docs:
You can create an attributed string from HTML data using the initialization methods initWithHTML:documentAttributes: and initWithHTML:baseURL:documentAttributes:. The methods return text attributes defined by the HTML as the attributes of the string. They return document-level attributes defined by the HTML, such as paper and margin sizes, by reference to an NSDictionary object, as described in “RTF Files and Attributed Strings.” The methods translate HTML as well as possible into structures of the Cocoa text system, but the Application Kit does not provide complete, true rendering of arbitrary HTML.
An alternative here would be to just use the available attributes, setting line indents and such according to the image size. I haven't worked with attributed strings at this level, so I the best reference would be the developer videos and the programming guide for NSAttributedString. https://developer.apple.com/library/mac/#documentation/Cocoa/Conceptual/AttributedStrings/AttributedStrings.html#//apple_ref/doc/uid/10000036-BBCCGDBG
For lesser versions of iOS, you'd probably be better off becoming familiar with CoreText. In the end you'll be rewarded with a better looking result, reusability/flexibility, the list goes on. For that, I would start with the CoreText programming guide: https://developer.apple.com/library/mac/#documentation/StringsTextFonts/Conceptual/CoreText_Programming/Introduction/Introduction.html
Maybe someone else can provide some sample code, but I think just looking through the docs will give you less of a headache than trying to calculate 4 labels like that.
EDIT:
I changed the link for CoreText
You have to go with CoreText: create your AttributedString and a CTFramesetter with it.
Then you can get a CTFrame for each of your textboxes and draw it in your graphics context.
https://developer.apple.com/library/mac/#documentation/Carbon/Reference/CTFramesetterRef/Reference/reference.html#//apple_ref/doc/uid/TP40005105
You can also use a UIWebView
I'm developing an iPad app that includes the ability to print a document. Some documents require rights management wherein a limited number of copies may be printed and the number of copies printed must be recorded.
I've scoured the UIPrintInteractionController documentation and have found no such capabilities. This question was asked here over a year ago: iOS Printing UI - limit number of copies and at the time this feature was not available - here's hoping it has since changed.
My questions are:
A year later, does cocoa touch still not have the ability to limit number of copies that can be printed?
Is there any way to GET the number of copies printed?
Is one forced to use the UIPrintInteractionController? If I'm unable to set or get copies, then I may be forced to write my own (if at all possible).
Trying to control the number of copies a user can print using UIPrintInteractionController.
I have the same problem and I was walking home and it hit me. Why dont I just create a category for the UIStepper and override its behavior.
I dont use the UIStepper in my app so this wont effect my app, but if you do theres probably a way you can selectively apply this code.
Anyway, you want something like this:
#implementation UIStepper (MJStepper)
- (id)initWithFrame:(CGRect)frame
{
self = [super initWithFrame:frame];
if (self) {
// Initialization code
self.minimumValue = 1;
self.maximumValue = 1;
}
return self;
}
#end
So create a category and include it in the same view which uses the UIPrintInteractionController
Then set the min and max values on init, and BAM. The print modal says 1 copy and has no uistepper. :)
You could set this to any number programmatically or even give the user a fixed range.
I really wish Apple had a full programmatic API for printing.
I am building a Kiosk app and the last thing I want is for the user to be able to print 100 copies of something.
I think the paper type and printer selection is still annoying but I can probably live with that.
Does anyone know if theres a way to control what Paper types your printer supports?
I know theres a delegate callback which I might be able to use to force a specific type of paper so I might try that.
Anyway, hope this helps! :)
I want to create a new object so as to instantiate and use it several times;
For example, if I want to create an object that has a label and a button inside, how do I? I created a new NSObject but inside it has nothing, then how do I make everything from scratch since there was a viewDidLoad for example (obviously, since it has a view)?
thanks!
Your questions lead me to think that you're really just starting out. There's nothing wrong with that, but rather than trying to summarize several megabytes of documentation in a few paragraphs, I'm just going to point you to the iOS Starting Point. I think that you're just trying to create a container that can hold other UI components? If so, use a UIView for that. However, don't jump in and try to get something specific done without first reading through some of the Getting Started documents -- you'll just end up back here, and we'll just point you back to the docs. You might like the Your First iOS Application guide, as that lets you get your feet wet but explains things along the way.