I am developing a security application which records a series of images and then uploads them to a server. I have a few problems through.
1 My picture capture code is working, but it is very slow, I have the takePicture() method inside onPictureCallback to take another picture, however I only get a couple pictures a minute, however if on the system camera app by clicking the shutter button very fast you can take pictures at a much higher speed, I thought my way would be the fastest possible, do you know how I can increase the the speed?
2 My upload code is also working, however im not sure how to create a upload que from the pictures taken. I have tried using a database, however the file comes back static and I can't put the then static URI into the database as the method won't accept a static variable. I can't use a standard array as I would like to be able to resume uploading if the phone restarts.
3 Lastly im only using taking pictures as their doen't seem to be a way to access frames while recording video. Is their some sort of way, to reocord video a low framerate, pause it get a frame put that in an upload que and then carry on recording?
Im just guessing that if you pause a video your saving it somewhere temporarily and carrying on afterwards.
I would be very grateful if I can get help with any of the 3 issues.
For problem number 2, try using a scheme that can handle concurrent connections like non-blocking sockets or something similar so that multiple images can be uploaded at once. This method would make the queueing scheme unnecessary.
If possible, I would recommend using a networking library like eventlet since it handles all of that ugly concurrent networking code for you.
Related
I want to make an android app, that records a video stream and when the user does not push a button, everything before the last 120 seconds of the video stream gets deleted. This should run for hours so only ~50mb are in use all the time. Has anyone an idea how to record a video like a never-ending flow of data that allows me to access certain points and delete everything before those points?
I know this question is pretty general but I find it very hard to access android camera close to the hardware.
You'll probably run into file size limitations if nothing else.
A better approach would be to just keep recording 30-second videos, and delete any that are more than two minutes old until the user presses the "record" button, at which time you start keeping them.
Then splice them together into one long video afterwards.
By the way, this will kill your battery. I assume you're equipped to deal with that.
I'm currently working on an app with the end goal of being roughly analogous to an Android version of Air Play for the iDevices.
Streaming media and all that is easy enough, but I'd like to be able to include games as well. The problem with that is that to do so I'd have to stream the screen.
I've looked around at various things about taking screenshots (this question and the derivatives from it in particular), but I'm concerned about the frequency/latency. When gaming, anything less than 15-20 fps simply isn't going to cut it, and I'm not certain such is possible with the methods I've seen so far.
Does anyone know if such a thing is plausible, and if so what it would take?
Edit: To make it more clear, I'm basically trying to create a more limited form of "remote desktop" for Android. Essentially, capture what the device is currently doing (movie, game, whatever) and replicate it on another device.
My initial thoughts are to simply grab the audio buffer and the frame buffer and pass them through a socket to the other device, but I'm concerned that the methods I've seen for capturing the frame buffer are too slow for the intended use. I've seen people throwing around comments of 3 FPS limits and whatnot on some of the more common ways of accessing the frame buffer.
What I'm looking for is a way to get at the buffer without those limitations.
I am not sure what you are trying to accomplish when you refer to "Stream" a video game.
But if you are trying to mimic AirPlay, all you need to do is connect via a Bluetooth/ internet connection to a device and allow sound. Then save the results or handle it accordingly.
But video games do not "Stream" a screen because the mobile device will not handle much of a work load. There are other problems like, how to will you handle the game if the person looses internet connection while playing? On top of that, this would require a lot of servers to support the game workload on the backend and bandwidth.
But if you are trying to create an online game. Essentially all you need to do is send and receive messages from a server. That is simple. If you want to "Stream" to another device, simply connect the mobile device to speakers or a TV. Just about all mobile video games or applications just send simple messages via JSON or something similar. This reduces overhead, is simple syntax, and may be used across multiple platforms.
It sounds like you should take a look at this (repost):
https://stackoverflow.com/questions/2885533/where-to-start-game-programming-for-android
If not, this is more of an open question about how to implement a video game.
I'm looking for the best way (if any...) to capture continuous video to a circular buffer on the SD card, allowing the user to capture events after they have happened.
The standard video recording API allows you to just write directly to a file, and when you reach the limit (set by the user, or the capacity of the SD card) you have to stop and restart the recording. This creates up to a 2 second long window where the recording is not running. This is what some existing apps like DailyRoads Voyager already do. To minimize the chance of missing something important you can set the splitting time to something long, like 10 minutes, but if an event occurs near the end of this timespan you are wasting space by storing the 9 minutes of nothing at the beginning.
So, my idea for now is as follows: I'll have a large file that will serve as the buffer. I'll use some code I've found to capture the frames and save them to the file myself, wrapping around at the end. When the user wants to keep some part, I'll mark it by pointers to the beginning and end in the buffer. The recording can continue as before, skipping over regions that are marked for retention.
After the recording is stopped, or maybe during that on a background thread (depending on phone/card speed) I'll copy out the marked region to another file and remove the overwrite protection.
Main question, if you don't care about the details above: I can't seem to find a way to convert the individual frames to a video file in the Android SDK. Is it possible? If not, are there any available libraries, maybe in native code, that can do this?
I don't really care about the big buffer of uncompressed frames, but the exported videos should be compressed in an Android-friendly format. But if there is a way to compress the buffer I would like to hear about it.
Thank you.
In Android's MediaRecorder there is two way to specify the output. One is a filename and another is a FileDescriptor.
Using static method fromSocket of ParcelFileDescriptor you can create an instance of ParcelFileDescriptor pointing to a socket. Then, call getFileDescriptor to get the FileDescriptor to be passed to the MediaRecorder.
Since you can get the encoded video from the socket (as if you were creating a local web server), you will be able to access individual frames of the video, although not so directly, because you will need to decode it first.
I've got an Android project I'm working on that, ultimately, will require me to create a movie file out of a series of still images taken with a phone's camera. That is to say, I want to be able to take raw image frames and string them together, one by one, into a movie. Audio is not a concern at this stage.
Looking over the Android API, it looks like there are calls in it to create movie files, but it seems those are entirely geared around making a live recording from the camera on an immediate basis. While nice, I can't use that for my purposes, as I need to put annotations and other post-production things on the images as they come in before they get fed into a movie (plus, the images come way too slowly to do a live recording). Worse, looking over the Android source, it looks like a non-trivial task to rewire that to do what I want it to do (at least without touching the NDK).
Is there any way I can use the API to do something like this? Or alternatively, what would be the best way to go about this, if it's even feasible on cell phone hardware (which seems to keep getting more and more powerful, strangely...)?
Is there any way I can use the API to
do something like this?
No.
Or alternatively, what would be the
best way to go about this, if it's
even feasible on cell phone hardware
(which seems to keep getting more and
more powerful, strangely...)?
It is possible you can find a Java library that lets you assemble movies out of stills and annotations, but I would be rather surprised if it met your needs, would run on Android, and would run acceptably on mobile phone hardware.
IMHO, the best route is to use a Web service. Use the device for data collection, use the server to do all the heavy lifting of assembling the movie out of the parts.
If you have to do it on-device, the NDK seems like the only practical route.
Do you just want to create movie files or do you want to display them on the phone?
If you just want to display the post-processed annotated images as a movie then it's possible. What is the format of your images ? Currently, I'm able to display to MJPEG video on a Nexus One (running 2.1) without any noticeable lag without using the NDK. In my case the images are coming from the network.
On the other hand, if you just want to create movie files and store is on the phone or some other place then CommonsWave's idea of "delegating" this to a server makes more sense since you will have more processing power and storage on the server. This will require that you have access to a network and don't mind sending all the images from the phone to the server and then download the movie file back to the phone.
I noticed that Flash allows you to insert cue's into a video file (flv). Is something like this possible on Android? I have a video that runs locally in my Android app and I would like to insert cues into the video which will give me callbacks when a certain portion of the video has been reached. If this is not possible, are there any other methods to do something similar? I have to be pretty precise with where the cue is located.
Thanks
Note:
I just found this same question on stackoverflow. Can anyone verify that this is still the case? (That it is not possible, only by polling the video continually). I did know of this way, but it's not the most accurate way if you need to be precise and stich dynamic pieces of video together seamlessly.
Android VideoView - Detect point of time in video
I´m working on this as well and a kind of cue/action scripts. For tutorials, instruction video I need to keep track of current position to serve for example questions and navigation menus appropriate for that point in time. Easy when it´s sufficient to act in response to user input but otherwise firing up a thread to poll at some decent interval is the thing. Accuracy might be acceptable and can be calibrated by sensing actual position.