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• Extract image of every frame of a video using react-native-ffmpeg

  1er octobre 2020, par EdG

  I have looked all over the internet to get a way to extract image of everyframe of a video using react-native-ffmpeg. I am making a mobile app and I want to show all per frame images on the video timeline. I want to do this natively on mobile so that I can utilise hardware power of mobile. That is the reason I am looking for react-native-ffmpeg kind of library. Am I in the right direction ? This npmjs.com/package/react-native-ffmpeg is what I am trying to use. I need to know the command to do the job.

  


• armv6 : Accelerate ff_imdct_half for general case (mdct_bits != 6)

  11 juillet 2014, par Ben Avison

  armv6 : Accelerate ff_imdct_half for general case (mdct_bits != 6)
  The previous implementation targeted DTS Coherent Acoustics, which only
  
  requires mdct_bits == 6. This relatively small size lent itself to
  
  unrolling the loops a small number of times, and encoding offsets
  
  calculated at assembly time within the load/store instructions of each
  
  iteration.
  In the more general case (codecs such as AAC and AC3) much larger arrays
  
  are used - mdct_bits == [8, 9, 11]. The old method does not scale for
  
  these cases, so more integer registers are used with non-unrolled versions
  
  of the loops (and with some stack spillage). The postrotation filter loop
  
  is still unrolled by a factor of 2 to permit the double-buffering of some
  
  VFP registers to facilitate overlap of neighbouring iterations.
  I benchmarked the result by measuring the number of gperftools samples
  
  that hit anywhere in the AAC decoder (starting from aac_decode_frame())
  
  or specifically in ff_imdct_half_c / ff_imdct_half_vfp, for the same
  
  example AAC stream :
                    Before          After
  
                    Mean   StdDev   Mean   StdDev  Confidence  Change
  
  aac_decode_frame  2368.1 35.8     2117.2 35.3    100.0%      +11.8%
  
  ff_imdct_half_*   457.5  22.4     251.2  16.2    100.0%      +82.1%
  Signed-off-by : Martin Storsjö <martin@martin.st>
  

  • [DBH] libavcodec/arm/mdct_vfp.S

• Raspberry Pi HDMI to Virtual Input Device using UV4L Raspidisp

  8 mai 2021, par Darshan Patel

  I'm trying to convert Raspberry pi hdmi as input device, and then I want to restream that using ffmpeg.
I have used below command to add input device.

  


  uv4l --driver raspidisp --display 0 --framerate 5 --resolution 0 --auto-video_nr


  


  It's showing below output when run.

  


  <notice> [core] Trying to loading driver &#x27;raspidisp&#x27; from built-in drivers...&#xA;<notice> [core] Loading driver &#x27;raspidisp&#x27; from external plug-in&#x27;s...&#xA;<notice> [driver] RaspiDisp Video4Linux2 Driver built Jan  6 2019&#xA;<notice> [core] Device detected!&#xA;<warning> [core] Cannot create /dev/video0 because file already exists&#xA;<warning> [core] Cannot create /dev/video1 because file already exists&#xA;<warning> [core] Cannot create /dev/video2 because file already exists&#xA;<notice> [core] Registering device node /dev/video3&#xA;</notice></warning></warning></warning></notice></notice></notice></notice>

  


  It is added as /dev/Video3.
Then I am trying to restream it using ffmpeg as below command.

  


  sudo ffmpeg -r 25 -s 1280x720 -f video4linux2 -i /dev/video3 -f mpegts udp://192.168.1.109:1234


  


  It gives below error.

  


  [video4linux2,v4l2 @ 0xe64200] The driver does not permit changing the time per frame
[video4linux2,v4l2 @ 0xe64200] Time per frame unknown
[video4linux2,v4l2 @ 0xe64200] mmap: No such device
/dev/video3: No such device


  


  Any help or suggestions greatly appreciated.