My application is for system administrators. One of the most needed features - is remote desktop monitoring. First way - is to grab screenshots and send them to admin. Second way - more interesting - grab desktop and stream it out over RTSP with libvlc. But it needs libvlccore and Plugins folder. Common size is over 68MB.
I'm sure that RTSP doesn't use all of plugins. Does anybody know how to build a single file with a minimal set of functions for streaming out (from vlc sources ofcourse)?
Related
According to AWS docs, preferred way to download files from S3 bucket is to use Amplify.Storage.downloadFile. (Or old one AWSS3TransferUtility)
It was mentioned in the "Cancel, Pause, Resume" section, that it uses NSURLSessionTask under the hood.
Question:
Is there any way to implement next scenario:
Start downloading big file. In case of network error / app closing / user interrupting / any_other_reason, keep downloaded file part and continue later - during next session?
does anyone know of best practices or common strategies in backend design for serving dynamic images and videos to client applications?
Background: I'm currently building an application that allows users to upload their own images and videos. I'm not really sure about how to serve these media files back to the client in the most efficient way. Do I store the files on the same VPS that my application server is running on? Do I need to save the files in different qualities / densities to better adjust for the clients' screen resolution? (I'll have mostly mobile clients)
I tried googling these questions but apparently I'm asking the wrong questions :-)
I would really appreciate maybe a reference or professional vocabulary on these topics.
Thanks in advance.
1) You need to split web server and application server.
First of all do not try to stream media files from your backend unless you can offload low-level stuff to OS - most likely you will do it wrong.
Use proxy server as an web server to serve such files.
nginx will do.
Also you need to have backup of your media files the same way as you do backup of your database.
Storing static huge media files along with application server is wrong move - it will not scale at all.
You can add cron task to move files to some CDN server - when your move is complete you replace URL in database to match new location.
So by using nginx you will save precious CPU and RAM while file is getting moved to external server.
And CDN will help you to dedicate bandwidth and CPU/RAM resources to application server.
2) Regarding image resolution and downsampling:
Screens of modern handsets have the same or even better resolution compared to typical office workstation.
Link speeds have much bigger impact on UX.
If client has smartphone with huge screen but with slow link you still have to deliver image or video as fast as possible even if quality of media will not be match the resolution of handset.
It makes sense to downsample images on demand and store result on disk for nginx/CDN to serve it again.
In case of videos it makes sense to make "bad" version with big compression(quality loss) for the cases of slow link - device will downsample it itself during playback.
And you can keep client statistics (screen sizes/downlink speeds) and generate optimized versions of such video file later when you see that it is "popular".
FYI: Several years ago some social meda giant dropped idea to prepare all possible versions of the same media file in favour of FPGA on-the-fly resampler.
I do not remember the name of the company and URL to the article. It was probably instagram.
Some cloud providers have offers with FPGA or CUDA on board to do heavy lifting.
So in some cases you could exchange storage for heave horsepower to do conversion on the fly.
I've created an Android Application and I've connected different watson services, available on Bluemix, to it: Natural Language Classifier, Visual Recognition and Speech to Text.
1) The first and the second work well; I've a little problem with the third one about the format of the audio. The app should register a 30sec audio, save it on memory and send to the service to obtain the corresponding text.
I've used an instance of the class MediaRecorder to register the file. It works, but the available Output formats are AAC_ADTS, AMR_WB, AMR_NB, MPEG_4, THREE_GPP, RAW_MR and WEBM.
The service, differently, accepts in input these formats: FLAC, WAV, PCM.
What is the best way to convert the audio file from the first set of outputs to the second one? Is there a simple method to do that? For example, from THREE_GPP or MPEG_4 to WAV or PCM.
I've googled searching infos and ideas, but I've found only few and long-time methods, not well understood.
I'm looking for a fast method, because I would make the latency of conversion and elaboration by the service as short as possible.
Is there an available library that does this? Or a simple code snippet?
2) One last thing:
SpeechResults transcript = service.recognize(audio, HttpMediaType.AUDIO_WAV);
System.out.println(transcript);
"transcript" is a json response. Is there a method to directly extract only the text, or should I parse the json?
Any suggestion will be appreciated!
Thanks!
To convert the audio records in different formats/encodings you could:
- find an audio encoder lib to include into your app which supports the required libs but it could very heavy to run on a mobile device (if you find the right lib)
- develop an external web application used to send your record, make it encoded and returned as a file or a stream
- develop a simple web application working like a live proxy that gets the record file, makes a live conversion of the file and send to Watson
Both the 2nd option and the 3rd one expects to use an encoding tool like ffmpeg.
The 3rd one is lighter to develop but a little bit more complex but could allow you to save 2 http request from you android device
I haven't found any way to automate inserting an ad spot into an existing live stream without stopping the streams and/or using a Flash client to interact with Wowza.
The idea is that these ads can be randomly chosen and inserted into the stream programatically & automated.
Can someone please point me in the right direction of how to properly change sources on the fly?
Thanks!
The following articles may be of interest for you
https://www.wowza.com/docs/how-to-switch-streams-using-stream-class-streams
https://www.wowza.com/docs/how-to-control-stream-class-streams-dynamically-modulestreamcontrol
https://www.wowza.com/docs/how-to-use-ipublishingprovider-api-to-publish-server-side-live-streams
I've previously created a custom module for Wowza that allows you to create an output stream from a live input stream, then control the output and switch between the live input stream and other live or on demand streams.
I have files and directories setup on a Windows network share (\foo). I want to be able to move the files into different directories (eg. \foo\bar\baz.txt --> \foo\quux\baz.txt) via an iPhone app.
However, having failed to find a solution I think it might be a better idea to write a separate program that runs on the server that handles moving the files and have the iPhone app as a client that issues instructions to the server about what files to move.
Any suggestions on this would be much appreciated.
Edit: Since someone has voted to close this for not being clear... the question is: I want to move files on a network share from one directory to the other.
How do I do this using Objective-C/Cocoa Touch/iPhone SDK?
To access the file shares directly, you would have to implement an SMB client. I suppose you could pilfer code from Samba's smbclient and see if you can get it building on the iPhone.
A big advantage to using a web service is that you can set it up for access outside your LAN. This is much harder with SMB unless you already have a VPN set up.
An in-between possibility that just occurred to me is to expose the shares via WebDAV on IIS. In fact, this is probably much easier that writing your own service.