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• DirectX12 Video Encoding : output buffer population

  6 janvier 2023, par mike

  I'm attempting to implement DX12 video encoding.

  


  

  • To date I've been using the ffmpeg library so am not very clued up on very low level data.

  


  • I'm using the simplest possible encoding I can think of, with GOP size of 1 and H264

  


  


  I am struggling with the first part of defining the output structure D3D12_VIDEO_ENCODER_ENCODEFRAME_OUTPUT_ARGUMENTS, namely setting up the resource pBuffer in D3D12_VIDEO_ENCODER_COMPRESSED_BITSTREAM :

  


  typedef struct D3D12_VIDEO_ENCODER_COMPRESSED_BITSTREAM {
  ID3D12Resource *pBuffer;
  UINT64         FrameStartOffset;
} D3D12_VIDEO_ENCODER_COMPRESSED_BITSTREAM;


  


  Regards pBuffer, the docs say :

  


  


  "A pointer to a ID3D12Resource containing the compressed bitstream buffer".

  


  


  

  • So I guess I create a buffer at least the size of the input frame + room for header data, and make it writeable - seems like it should be straightforward, but am I missing something ? Should it be multi-planar for example, or be some multiple of input frame size ?
    

  


  


  Then :
  

  


  


  "The output bitstream is expected to contain the subregion headers, but not the picture, sequence, video or other headers. The host is responsible for coding those headers and generating the complete bitstream."
  

  


  


  

  • what do these subregion headers look like ? I am showing my lack of encoding knowledge here in general, is there a resource somewhere explaining how to calculate them ? (or have I misread this, and this is saying the output will contain them)

  


  • do I just write them by copying into mapped memory and setting the FrameStartOffset to point after the header data ?

  


  • I'm currently streaming AVPackets from ffmpeg using libdatachannel, how would the content of the output (without my adding extra headers) compare to an AVPacket->data ?

  


  


• How can I make windows "like" the mp4 files I create in Linux and sync with Rsync

  17 juillet 2019, par Geoff Fox

  I am a meteorologist on TV remotely from a studio I built. My control room uses a TriCaster, an amazing studio-in-a-box which runs on a Windows 7 variant. I make my weather maps myself on a Centos 7 machine — around 40,000/day.

  I don’t entirely understand the problem, but here’s a quote from someone helping me at NewTek (the TriCaster company)

  Rsync is built on a *nix based environment where all the file permissions and attributes are based on the Linux environment. There is no meaning for this in NTFS and Windows. The result is you get files that will most likely have the read-only flag set or no flag at all. Other attributes will be delivered as null. I’m sure from your own programming experience, programs don’t like null values and they generally have to be accounted for very specifically.

  And so the finely tuned TriCaster stumbles, meaning lost frames or other problems caused by my short weather animations.

  Here are some samples of the Rsync code I use

  rsync -r -t -s -v --no-p --chmod=ugo=rwX /var/www/html/output/loops/mp4/conus*.mp4 /mnt/tricaster/Clips/Import
rsync -r -t -s -v --no-p --chmod=ugo=rwX /var/www/html/output/loops/mp4/nebraska*.mp4 /mnt/tricaster/Clips/Import
rsync -r -t -s -v --no-p --chmod=ugo=rwX /var/www/html/output/loops/mp4/northernplains*.mp4 /mnt/tricaster/Clips/Import

  These are mp4 files. They are only used locally. I really don’t care what flags are checked and permissions filled as long as Windows 7 doesn’t care.

  At this point I always like to tell folks, though I do write some code my last computer class was in high school,’67-68 semester. Thanks in advance for your help.

• what codec to specify to accessing my HDMI-to-USB adaptor, under Linux ? [closed]

  14 mai 2022, par David

  A week or so ago,I bought a HDMI-to-USB adapter, to use to capture video
TV content from my TV's set-top box. (Xfinity, if it matters. Box generically is :
"XiD X1"...I have both the Pace and the Cisco models available here in this house.)

  


  Specifically, here's the adapter I bought,from Amazon :
https://www.amazon.com/gp/product/B09FLN63B3

  


  So, I'm fluent in both Windows (Win-11) and Linux (Debian 'Bullseye', on my chromebook).

  


  The adapter does not come with any recommendations for what software/drivers to (try to) use, but I was prepared for that.
After some google searches, I decided to first try using the cmd-line
'ffmpeg' program, because I'm
quite familiar with that (excellent !) piece of open-source software !

  


  So, after a day or two of (mostly) success recordings under Win-11, using
ffmpeg's Microsoft-based 'dshow' (aka 'DirectShow'), I decided to attempt to get
up to the same level of accomplishment on my Chromebook, under Linux, also
using 'ffmpeg'.

  


  [Ok...a very brief explanation of 'mostly' successful. I'll
post another separate question here, about the specifics of my glitches,
using 'dshow' on Windows. But, essentially, when I try to record to a MP4
file, I get 2 scenarios of glitch : #1 : Suddenly, dropped packets surges up,
and I get "1000 dropped' yellow msg #2 : On other trials, I get '...contains
no image...'.) So, I figured I should first give a Linux a chance,
before spending more effort trying to resolve the glitches on Windows.]

  


  My first snag, was learning that 'dshow' seems to be specific to 'Windows',
and thus ffmpeg is getting 'unknown' for my reference to 'dshow'. After more hours of 'guessing', I've finally learned/concluded that there are other things
(something call "DeckLink" is one such alternative ?) for Linux, but I'm unclear
what extra Linux packages might exist for ffmpeg support, or whether I will need to built a more complete 'ffmpeg' (e.g. from source code), to get things going under Linux ?

  


  Is my device able to be accessed from some tools other than 'ffmpeg' ?
(e.g. VLC or Handbrake or whatever ?) more easily, on the Linux platform ?

  


  [If I had to, I'd probably invest another $20-$50 in some other hardware
device that goes from HDMI-to-USB (USB-A/B), if it were ]

  


  All ideas are welcome...(TIA)

  


  — Dave