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• Generate AcoustID/Chromaprint acoustic fingerprint in iOS

  20 janvier 2017, par ev0lution

  Chromaprint is an open-source software library for calculating an AcoustID audio fingerprint of an audio file.

  I’m trying to generate this audio fingerprint from a local file on iOS.

  The library can be built on Windows, Linux and OS X, where it creates a dynamic library as well as a standalone program (fpcalc) that accepts an audio file, decodes the audio and passes it to the chromaprint library to calculate the fingerprint. It doesn’t really work on iOS for the following reasons :

  1. The standalone fpcalc program can’t be run on iOS because you can’t run an executable from an app
  2. The source code to the fpcalc program uses chromaprint and ffmpeg. From what I’ve read, ffmpeg is difficult to compile on iOS. The chromaprint docs state that the Accelerate framework can be used in OS X/iOS, but there is no example code to do this and I have no idea where to start.

  I’ve been having a bit of trouble actually building the library for iOS (CMake hates me), but I feel like the above problems are more relevant because even with the library compiled, it wouldn’t just work out of the box.

  I’m trying to avoid this being a "write my code for me" question, but I am very much stuck on essentially every aspect of generating a chromaprint fingerprint for iOS.

  My goal, I think, is to recreate the functionality of the fpcalc program on iOS - to decode an audio file (stored on the device, of any audio type) and pass it to the chromaprint library to generate the fingerprint.

  I found this question about acoustic fingerprinting on iOS but it wasn’t relevant to chromaprint/AcoustID and the answers were less than helpful. Echoprint Codegen is interesting, but I need a chromaprint fingerprint.

• Prevent suspend event when streaming video via HTML video tag

  24 septembre 2014, par jasongullickson

  I seem to be having the opposite problem of most people who are streaming video using the HTML video tag ; I’m saturating the client with data.

  When playing a long video served via ffserver (webm container) everything works great but eventually the browser (Chrome in this case) will begin throwing "suspend" events. After a number of these ( 50-100), a "stalled" event will fire and playback will stop.

  I believe the problem is that once Chrome has buffered a certain amount of video it goes into "suspend" and stops downloading more data. I’ve tested this theory by throttling the speed at which video data is delivered, and if I keep the delivered frame rate close to the playback rate, I can prevent this from happening, but of course deliberately holding back server performance isn’t ideal.

  What I’m looking for is either a way to suppress this "suspend" behavior altogether, or alternatively a way to respond to the event that prevents the eventual "stalled" state.

  Presumably the browser at some point exits the "suspend" state and begins requesting data again, but I haven’t actually observed this occurring. I’m using a chain of mpeg2 -> ffmpeg -> ffserver to stream the video so if the browser is attempting to resume loading data I don’t see the request in my application. I could use a proxy or a sniffer to watch for the traffic but I would expect that maybe there is an ffserver log that can tell me the same thing ? In any event if it’s attempting to resume the download it’s failing, and there’s no indication server-side that there’s a reason for the request to fail (in fact I can pull up the same video feed from ffserver and see it playing correctly).

  So I feel like I’ve isolated this to a client-side playback issue, and one where the browser is voluntarily giving up on loading the data, but I’m not sure how to convince it to "not do that", or at least attempt to resume when it runs the buffer dry.

• Code library for image processing [on hold]

  1er septembre 2014, par user3928079

  Dear Stack Overflow Users,

  I am looking to create my programming portfolio as a graduate of Kennesaw State University by July 2015, when I graduate. I want to create at least 3 cross platform programs related to video or animation. In the package there will be a program for playing video and music files, a program for converting video and music files, and either a program upscaling video and image files or a program that helps animators create animation like Flipbook Pro. Since Java is cross platform, and Java is the language I’m more comfortable with, I’ll develop the software in Java, unless of course Python is cross platform as well. May you please recommend me some image processing libraries that will help me accomplish the development of these types of software programs. For the upscaling program, an upscaling algorithm from BenVista called S-Spline Max is needed, especially since I want to preserve the detail of the image, because in upscaling, you are unable to gain new information from the original information. What are some good image processing libraries I can use. I know of OpenCV, but what do a lot of programs use, high profile or low profile, like Adobe Premiere Pro or Davinci Resolve. FFMPEG is a good video library, but can it easily accomplish what I need ? What are some others that can help me in my 11 month long quest ?

  Regards,

  Jordan White