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• embed video stream with custom meta data

  15 mai 2022, par Sergey Kolesnik

  I have an optical system that provides a UDP video stream.

  


  From device specification FAQ :

  


  


  Both single metadata (KLV) stream and compressed video (H.264) with metadata (KLV) are available on Ethernet link. Compressed video and metadata are coupled in the same stream compliant with STANAG 4609 standard. Each encoded video stream is encapsulated with the associated metadata within an MPEG-TS single program stream over Ethernet UDP/IP/ The video and metadata are synchronized through the use of timestamps.

  


  


  Also there are other devices that provide data about the state of an aircraft (velocity, coords, etc). This data should be displayed on a client GUI display alongside with video. Of course it has to be synchronized with the current video frame.

  


  One of the approaches I though of is to embed this data into the video stream. But I am not sure if it is possible or should I use another (than UDP) protocol for this purpose.

  


  Is it possible/reasonable to use such approach ? Is ffmpeg library suitable in this case ?
If not, what are the other ways to synchronize data with a video frame.
Latency is crucial. Although bandwidth is limited to 2-5 Mbps.

  


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  It seems to be possible using ffmpeg : AVPacket can be provided with additional data using function av_packet_add_side_data which takes a preallocated buffer, size and a type AVPacketSideDataType.
However, I am not sure for now, which enum value of AVPacketSideDataType can be used for custom user-provided binary data.

  


  Something similar that might be used for my needs :

  


  How do I encode KLV packets to an H.264 video using libav*

  


• FFMPEG API — How much do stream parameters change frame-to-frame ?

  8 septembre 2015, par kacey

  I’m trying to extract raw streams from devices and files using ffmpeg. I notice the crucial frame information (Video : width, height, pixel format, color space, Audio : sample format) is stored both in the AVCodecContext and in the AVFrame. This means I can access it prior to the stream playing and I can access it for every frame.

  How much do I need to account for these values changing frame-to-frame ? I found https://ffmpeg.org/doxygen/trunk/demuxing__decoding_8c_source.html#l00081 which indicates that at least width, height, and pixel format may change frame to frame.

  • Will the color space and sample format also change frame to frame ?
  • Will these changes be temporary (a single frame) or lasting (a significant block of frames) and is there any way to predict for this stream which behavior will occur ?
  • Is there a way to find the most descriptive attributes that this stream is possible of producing, such that I can scale all the lower-quality frames up, but not offer a result that is mindlessly higher-quality than the source, even if this is a device or a network stream where I cannot play all the frames in advance ?

  The fundamental question is : how do I resolve the flexibility of this API with the restriction that raw streams (my output) do not have any way of specifying a change of stream attributes mid-stream. I imagine I will need to either predict the most descriptive attributes to give the stream, or offer a new stream when the attributes change. Which choice to make depends on whether these values will change rapidly or stay relatively stable.

• Using a Web-based installer to retrieve (not distribute) 3rd party GPL or non-free software

  25 août 2013, par user1493918

  I am developing a software product which is able to communicate over a command line interface with GPL-covered software (specifically, my software can feed commands to FFMpeg). I understand that a crucial aspect of the GPL license is whether or not you distribute GPL-covered applications. My goal is to allow my users to have a seamless experience installing both my software and 3rd party GPL software. But I am trying to do this without my software actually including the the 3rd party (GPL-covered) software. To do this I am considering Web-based installers. I could use a Web-based installer to allow the end-user the option to retrieve a GPL-covered or non-free software app from a totally different server, independent of my own and outside my control. The user would be the one to install the software simply by making a decision (i.e. pressing "Next" in my installer). If they chose to do so, then my software's Web-based installer would retrieve the 3rd-party software, decompress and install it, then move on to installing my own application. In this way, my installer doesn't ship any GPL-covered or non-free software, and yet from the user's perspective all they had to do is click Next... Next... Next... Done !

  I have read about the GPL allowing you to distribute GPL-covered apps as part of an "aggregate..."
  http://www.gnu.org/licenses/gpl-faq.html#MereAggregation

  ...but this scenario isn't that. It's allowing the user to retrieve applications or libraries at his own discretion, using his own bandwidth, downloading from a server that has nothing to do with me.

  I can't seem to find information anywhere about the GPL-related licensing implications of using a Web-based installer. My goal is simply to give the end user every high-quality transcoding option possible within FFMpeg without stepping on anybody's toes legally.

  Possible ? If so then I'm hoping someone might be able to point me to a software installer program that would facilitate this. Thank you in advance for any replies.