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• Sending per frame metadata with H264 encoded frames

  21 septembre 2013, par user2459280

  We're looking for a way to send per frame metadata (for example an ID) with H264 encoded frames from a server to a client.

  We're currently developing a remote rendering application, where both client and server side are actively involved.
  The server renders a high quality image with all effects, lighting etc.
  The client also has model-informations and renders a diffuse image that is used when the bandwidth is too low or the images have to be warped in order to avoid stuttering .

  So far we're encoding the frames on the server side with ffmpeg and streaming them with live555 to the client, who receives an rtsp-stream and decodes the frames again using ffmpeg.

  For our application, we now need to send per frame metadata.
  We want the client to tell the server where the camera is right now.
  Ideally we'd be able to send the client's view matrix to the server, render the corresponding frame and send it back to the client together with its view matrix. So when the client receives a frame, we need to know exactly at what camera position the frame was rendered.

  Alternatively we could also tag each view matrix with an ID, send it to the server, render the frame and tag it with the same ID and send it back. In this case we'd have to assign the right matrix to the frame again on the client side.

  After several attempts to realize the above intent with ffmpeg we came to the conclusion that ffmpeg does not provide the required functionality. ffmpeg only provides a fix, predefined set of fields for metadata, that either cannot store a matrix or can only be set for every key frame, which is not frequently enough for our purpose.

  Now we're considering using live555. So far we have an on demand Server, witch gets a VideoSubsession with a H264VideoStreamDiscreteFramer to contain our own FramedSource class. In this class we load the encoded AVPacket (from ffmpeg) and send its data-buffer over the network. Now we need a way to send some kind of metadata with every frame to the client.

  Do you have any ideas how to solve this metadata problem with live555 oder another library ?

  Thanks for your help !

• Troll spirit

  15 juin 2013, par Mans — Law and liberty

  Last week’s announcements from the White House of steps being taken to begin fighting back against patent trolls, along with legislation passed in Vermont for the same purpose, are worthy of praise. Whether they prove effective or not, they are a sign of the problem finally having been recognised by the highest authorities. That said, only one aspect of the issue is addressed, that of non-practising entities or trolls. Little effort is being made to stymie troll-like behaviour from otherwise legitimate actors. While a stake is driven through the heart of the troll, its spirit remains free to roam the corporate world, and like a demon of darkness it possesses companies, compelling them to engage in the very practices we seek to eradicate.

  The demon

  The most damaging, when wielded by a troll, are those patents with vague or overly broad claims. These can easily be asserted against large numbers of alleged infringers, many of which likely choose to settle out of court rather than risk an expensive litigation process with uncertain outcome. Such negotiations are frequently subject to non-disclosure agreements prohibiting publication of details in any deals, or even the existence thereof. As a result, an accused has no way of assessing a fair price for a licence (assuming the patent is in fact valid), and the patent holder can thus extract from each would-be infringer precisely as much as they are willing or able to pay to avoid a lawsuit.

  At the root of this problem is the ease with which applications for the patents in question are granted. Given the volume of patent applications, it is hardly reasonable to demand a hugely more extensive examination process than currently takes place (although some improvements here are no doubt possible) ; after all, a speedy decision is in the best interest of all parties. The solution must evidently be found elsewhere.

  The exorcism

  An obvious cure to the problem is the abolishment of the patent system. As this is clearly not feasible today, more practical, albeit less effective, remedies must be sought. A few ideas follow.

  Make patent validity all or nothing

  Change the rules such that any claim being found invalid cancels the patent its entirety. With the full patent at stake in this manner, companies would be discouraged from gambling on frivolous claims and encouraged to conduct a more thorough background investigation before filing.

  Maintain a registry of licences

  Require that all patent licence agreements be filed in an open, easily searchable registry. This would hopefully increase fairness in licensing deals.

  Mandate reimbursement of licence fees for invalidated patents

  If a patent is challenged and found invalid, require that the owner reimburse any licence fees previously collected for the patent in question. Apart from being morally right, this could act as a deterrent to over-charging. The amount requested for a licence would likely be balanced against the risk of being made to pay it all back later, resulting in lower licence fees for low-confidence patents.

  These suggestions, alone or together, will not completely eradicate the problems of patent abuse. They are but small steps towards a more thorough overhaul of a system increasingly ill-suited to the nature and pace of modern technological development.

• Is there a way to Extract frames from .ts files with Http Live Stream in iOS

  12 mai 2016, par user1529412

  I have a current setup in iOS app that streams directly from RTSP and I use ffmpeg library in objective C to extract frames and convert them to RGB/YUV and display them consecutive RGB pics (Video like).

  I have a new requirement for HTTP Live Stream (HLS) which requires .ts files and m3u8 index file. I can play the ts files with AVPlayer, but its not what I am looking for, I want to apply my custom OpenGL View like the baove RTSP, so I need access to the actual frames of the ts, because I need the finer control over the frames to apply some OpenGL manipulation. Does anyone know how I can get at the frames of the .ts in Objective-C ?