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• UVC webcam with ffplay outputs only noise ?

  1er mars 2024, par Abdulla Masud

  (My end goal is to use a UVC webcam with esp32 or raspberry pi. I was hoping to learn while doing some fun projects.)

  


  I have an old UVC webcam (Creative model ct6840) but I can't seem to get it to work with ffplay. I have tried looking through the documentation and other questions here but nothing is working for me. So far I have only been able to achieve a noisy-jittery output.

  


  Running ffplay -f rawvideo -video_size 670x480 /dev/video1, I get :

  


  

  


  Can someone help me understand how to make the camera work with ffplay ?

  


  The following is the information of my webcam :

  


  $ ffmpeg -f v4l2 -list_formats all -i /dev/video2

  


  [video4linux2,v4l2 @ 0x17eb3c0] Compressed: Unsupported :          GSPCA OV511 : 320x240 640x480


  


  $ v4l-info /dev/video2

  


  ### v4l2 device info [/dev/video2] ###
general info
    VIDIOC_QUERYCAP
    driver                  : "ov519"
    card                    : "USB Camera (05a9:0511)"
    bus_info                : "usb-0000:00:14.0-8.2"
    version                 : 6.1.79
    capabilities            : 0x85200001 [VIDEO_CAPTURE,?,READWRITE,STREAMING,(null)]

standards

inputs
    VIDIOC_ENUMINPUT(0)
    index                   : 0
    name                    : "ov519"
    type                    : CAMERA
    audioset                : 0
    tuner                   : 0
    std                     : 0x0 []
    status                  : 0x0 []

video capture
    VIDIOC_ENUM_FMT(0,VIDEO_CAPTURE)
    index                   : 0
    type                    : VIDEO_CAPTURE
    flags                   : 1
    description             : "GSPCA OV511"
    pixelformat             : 0x3131354f [O511]
    VIDIOC_G_FMT(VIDEO_CAPTURE)
    type                    : VIDEO_CAPTURE
    fmt.pix.width           : 640
    fmt.pix.height          : 480
    fmt.pix.pixelformat     : 0x3131354f [O511]
    fmt.pix.field           : NONE
    fmt.pix.bytesperline    : 640
    fmt.pix.sizeimage       : 614400
    fmt.pix.colorspace      : JPEG
    fmt.pix.priv            : 4276996862

controls
    VIDIOC_QUERYCTRL(BASE+0)
    id                      : 9963776
    type                    : INTEGER
    name                    : "Brightness"
    minimum                 : 0
    maximum                 : 255
    step                    : 1
    default_value           : 127
    flags                   : 48
    VIDIOC_QUERYCTRL(BASE+1)
    id                      : 9963777
    type                    : INTEGER
    name                    : "Contrast"
    minimum                 : 0
    maximum                 : 255
    step                    : 1
    default_value           : 127
    flags                   : 32
    VIDIOC_QUERYCTRL(BASE+2)
    id                      : 9963778
    type                    : INTEGER
    name                    : "Saturation"
    minimum                 : 0
    maximum                 : 255
    step                    : 1
    default_value           : 127
    flags                   : 32
    VIDIOC_QUERYCTRL(BASE+24)
    id                      : 9963800
    type                    : MENU
    name                    : "Power Line Frequency"
    minimum                 : 0
    maximum                 : 2
    step                    : 1
    default_value           : 0
    flags                   : 0
    VIDIOC_QUERYCTRL(BASE+32)
    id                      : 9963808
    type                    : BOOLEAN
    name                    : "Brightness, Automatic"
    minimum                 : 0
    maximum                 : 1
    step                    : 1
    default_value           : 1
    flags                   : 8


  


  Can someone guide me here please ? Any advice will be greatly appreciated 

  


  (P.S. the camera works perfectly with "guvcview" gtk application but since I want to use the camera with raspberry pi, I want it to work with ffplay...)

  


• How to encode video with ffmpeg using AMD h264_amf

  10 novembre 2022, par Ivy Growing

  Given :

  


  

  • Win10

  


  • AMD CPU

  


  • Video capturing card Avermedia Live Gamer Extreme 3

  


  • ffmpeg versions and encoders :

  


  


  >ffmpeg.exe -encoders | find "264"
ffmpeg version 5.1-full_build-www.gyan.dev Copyright (c) 2000-2022 the FFmpeg developers
// cut
 V....D libx264              libx264 H.264 / AVC / MPEG-4 AVC / MPEG-4 part 10 (codec h264)
 V....D libx264rgb           libx264 H.264 / AVC / MPEG-4 AVC / MPEG-4 part 10 RGB (codec h264)
 V....D h264_amf             AMD AMF H.264 Encoder (codec h264)
 V....D h264_mf              H264 via MediaFoundation (codec h264)
 V....D h264_nvenc           NVIDIA NVENC H.264 encoder (codec h264)
 V..... h264_qsv             H.264 / AVC / MPEG-4 AVC / MPEG-4 part 10 (Intel Quick Sync Video acceleration) (codec h264)


  


  Required to capture the video into H.264 encoded file using AMD's hardware accelerator in the CPU (AMF, or VCE).
Tried : ffmpeg -y -f dshow -rtbufsize 2002000k -framerate 30 -i video="Live Gamer EXTREME 3"  -t 00:00:10  -c:v h264_amf output.ts
Result :

  


  Input #0, dshow, from 'video=Live Gamer EXTREME 3':
  Duration: N/A, start: 88548.973998, bitrate: N/A
  Stream #0:0: Video: rawvideo (YUY2 / 0x32595559), yuyv422(tv, bt709/bt709/unknown), 1280x720, 30 fps, 30 tbr, 10000k tbn
Stream mapping:
  Stream #0:0 -> #0:0 (rawvideo (native) -> h264 (h264_amf))
Press [q] to stop, [?] for help
[h264_amf @ 000002404328c700] DLL amfrt64.dll failed to open
Error initializing output stream 0:0 -- Error while opening encoder for output stream #0:0 - maybe incorrect parameters such as bit_rate, rate, width or height
Conversion failed!


  


  For some reason ffmpeg uses resolution 1280x720... When trying to specifiy the capture card resolution the following error appears :

  


  >ffmpeg -y -f dshow -rtbufsize 2002000k -framerate 30 -video_size 3840x2160 -i video="Live Gamer EXTREME 3" -r 30 -t 00:00:10   -c:v h264_amf -f mpegts output.ts
//cut
[dshow @ 0000029d7c0f84c0] Could not set video options
video=Live Gamer EXTREME 3: I/O error


  


  This is not unique error for Avermedia card. The same error appears with Dell web cam and for Magewell.

  


  From this answer the extra flags to be used with h264_amf. I guessed the default values should be good enough. It seems something needs to be configured or initialized when using AMF/VCE.

  


  The video encoding in software (without AMF) works just fine but loads the CPU. The goal is using dedicated hardware module and release computational power of the CPU for the other apps.

  


  Command example will be appreciated.

  


• Hacking the Popcorn Hour C-200

  3 mai 2010, par Mans — Hardware, MIPS

  Update : A new firmware version has been released since the publication of this article. I do not know if the procedure described below will work with the new version.

  The Popcorn Hour C-200 is a Linux-based media player with impressive specifications. At its heart is a Sigma Designs SMP8643 system on chip with a 667MHz MIPS 74Kf as main CPU, several co-processors, and 512MB of DRAM attached. Gigabit Ethernet, SATA, and USB provide connectivity with the world around it. With a modest $299 on the price tag, the temptation to repurpose the unit as a low-power server or cheap development board is hard to resist. This article shows how such a conversion can be achieved.
  

  Kernel

  The PCH runs a patched Linux 2.6.22.19 kernel. A source tarball is available from the manufacturer. This contains the sources with Sigma support patches, Con Kolivas’ patch set (scheduler tweaks), and assorted unrelated changes. Properly split patches are unfortunately not available. I have created a reduced patch against vanilla 2.6.22.19 with only Sigma-specific changes, available here.

  The installed kernel has a number of features disabled, notably PTY support and oprofile. We will use kexec to load a more friendly one.

  As might be expected, the PCH kernel does not have kexec support enabled. It does however, by virtue of using closed-source components, support module loading. This lets us turn kexec into a module and load it. A patch for this is available here. To build the module, apply the patch to the PCH sources and build using this configuration. This will produce two modules, kexec.ko and mips_kexec.ko. No other products of this build will be needed.

  The replacement kernel can be built from the PCH sources or, if one prefers, from vanilla 2.6.22.19 with the Sigma-only patch. For the latter case, this config provides a minimal starting point suitable for NFS-root.

  When configuring the kernel, make sure CONFIG_TANGOX_IGNORE_CMDLINE is enabled. Otherwise the command line will be overridden by a useless one stored in flash. A good command line can be set with CONFIG_CMDLINE (under “Kernel hacking” in menuconfig) or passed from kexec.

  Taking control

  In order to load our kexec module, we must first gain root privileges on the PCH, and here a few features of the system are working to our advantage :

  1. The PCH allows mounting any NFS export to access media files stored there.
  2. There is an HTTP server running. As root.
  3. This HTTP server can be readily instructed to fetch files from an NFS mount.
  4. Files with a name ending in .cgi are executed. As root.

  All we need do to profit from this is place the kexec modules, the kexec userspace tools, and a simple script on an NFS export. Once this is done, and the mount point configured on the PCH, a simple HTTP request will send the old kernel screaming to /dev/null, our shiny new kernel taking its place.

  The rootfs

  A kernel is mostly useless without a root filesystem containing tools and applications. A number of tools for cross-compiling a full system exist, each with its strengths and weaknesses. The only thing to look out for is the version of kernel headers used (usually a linux-headers package). As we will be running an old kernel, chances are the default version is too recent. Other than this, everything should be by the book.

  Assembling the parts

  Having gathered all the pieces, it is now time to assemble the hack. The following steps are suitable for an NFS-root system. Adaptation to a disk-based system is left as an exercise.

  1. Build a rootfs for MIPS 74Kf little endian. Make sure kernel headers used are no more recent than 2.6.22.x. Include a recent version of the kexec userspace tools.
  2. Fetch and unpack the PCH kernel sources.
  3. Apply the modular kexec patch.
  4. Using this config, build the modules and install them as usual to the rootfs. The version string must be 2.6.22.19-19-4.
  5. From either the same kernel sources or plain 2.6.22.19 with Sigma patches, build a vmlinux and (optionally) modules using this config. Modify the compiled-in command line to point to the correct rootfs. Set the version string to something other than in the previous step.
  6. Copy vmlinux to any directory in the rootfs.
  7. Copy kexec.sh and kexec.cgi to the same directory as vmlinux.
  8. Export the rootfs over NFS with full read/write permissions for the PCH.
  9. Power on the PCH, and update to latest firmware.
  10. Configure an NFS mount of the rootfs.
  11. Navigate to the rootfs in the PCH UI. A directory listing of bin, dev, etc. should be displayed.
  12. On the host system, run the kexec.sh script with the target hostname or IP address as argument.
  13. If all goes well, the new kernel will boot and mount the rootfs.

  Serial console

  A serial console is indispensable for solving boot problems. The PCH board has two UART connectors. We will use the one labeled UART0. The pinout is as follows (not standard PC pinout).

          +-----------+
         2| * * * * * |10
         1| * * * * * |9
          -----------+
            J7 UART0
      /---------------------/ board edge
  

  Pin	Function
  1	+5V
  5	Rx
  6	Tx
  10	GND

  The signals are 3.3V so a converter, e.g. MAX202, is required for connecting this to a PC serial port. The default port settings are 115200 bps 8n1.