Sur d’autres sites (7943)

• Extracting multiple video streams using FFmpeg

  11 avril 2023, par Ashutosh Singla

  I have a video file that contains 4 streams, 3 videos streams and one steam for metadata.

  


  Stream Info :

  


  Input #0, matroska,webm, from 'output_master.mkv':
Metadata:
title           : Azure Kinect
encoder         : libmatroska-1.4.9
creation_time   : 2021-05-20T12:11:15.000000Z
K4A_DEPTH_DELAY_NS: 0
K4A_WIRED_SYNC_MODE: MASTER
K4A_COLOR_FIRMWARE_VERSION: 1.6.110
K4A_DEPTH_FIRMWARE_VERSION: 1.6.79
K4A_DEVICE_SERIAL_NUMBER: 000123102712
K4A_START_OFFSET_NS: 298800000
Duration: 00:00:40.03, start: 0.000000, bitrate: 480934 kb/s

Stream #0:0(eng): Video: mjpeg (Baseline) (MJPG / 0x47504A4D), yuvj422p(pc, bt470bg/unknown/unknown), 2048x1536, SAR 1:1 DAR 4:3, 30 fps, 30 tbr, 1000k tbn (default)
Metadata:
  title           : COLOR
  K4A_COLOR_TRACK : 14499183330009048
  K4A_COLOR_MODE  : MJPG_1536P
Stream #0:1(eng): Video: rawvideo (b16g / 0x67363162), gray16be, 640x576, SAR 1:1 DAR 10:9, 30 fps, 30 tbr, 1000k tbn (default)
Metadata:
  title           : DEPTH
  K4A_DEPTH_TRACK : 429408169412322196
  K4A_DEPTH_MODE  : NFOV_UNBINNED
Stream #0:2(eng): Video: rawvideo (b16g / 0x67363162), gray16be, 640x576, SAR 1:1 DAR 10:9, 30 fps, 30 tbr, 1000k tbn (default)
Metadata:
  title           : IR
  K4A_IR_TRACK    : 194324406376800992
  K4A_IR_MODE     : ACTIVE
Stream #0:3: Attachment: none
Metadata:
  filename        : calibration.json
  mimetype        : application/octet-stream
  K4A_CALIBRATION_FILE: calibration.json


  


  I am using this command to extract the first stream :

  


  ffmpeg -i output_master.mkv -c copy  -map 0:v:0 out_1.mkv


  


  For the other two streams, I am using this command :

  


  ffmpeg -i output_master.mkv -c:v ffv1 -pix_fmt gray16be -allow_raw_vfw 1 -map 0:v:1 out_2.mkv
ffmpeg -i output_master.mkv -c:v ffv1 -pix_fmt gray16be -allow_raw_vfw 1 -map 0:v:2 out_3.mkv


  


  I do not know if I am using the right commands to extracting the video streams.

  


• ffmpeg overlay png on video has color issue

  9 janvier 2023, par Richard

  Im trying a simple overlay command to put a logo on a black video, but find the color a little different in output, the original RGB value of green part of the logo is (0,220,90), but changed to (0,191,88) in output. Looks like the color gets mixed with the black background, any ideas ?

  


  original logo rgb :

  


  

  


  rgb after logo overlayed on video :

  


  

  


  the command to overlay :

  


  ffmpeg -i video.mp4 -i logo.png -filter_complex "[1:v]format=rgba[s],[0:v][s]overlay=240:1275:format=auto" output.mp4


  


  the logo and video :

  


  ▶ ffmpeg -i logo.png               
ffmpeg version 4.4-static https://johnvansickle.com/ffmpeg/  Copyright (c) 2000-2021 the FFmpeg developers
  built with gcc 8 (Debian 8.3.0-6)
  configuration: --enable-gpl --enable-version3 --enable-static --disable-debug --disable-ffplay --disable-indev=sndio --disable-outdev=sndio --cc=gcc --enable-fontconfig --enable-frei0r --enable-gnutls --enable-gmp --enable-libgme --enable-gray --enable-libaom --enable-libfribidi --enable-libass --enable-libvmaf --enable-libfreetype --enable-libmp3lame --enable-libopencore-amrnb --enable-libopencore-amrwb --enable-libopenjpeg --enable-librubberband --enable-libsoxr --enable-libspeex --enable-libsrt --enable-libvorbis --enable-libopus --enable-libtheora --enable-libvidstab --enable-libvo-amrwbenc --enable-libvpx --enable-libwebp --enable-libx264 --enable-libx265 --enable-libxml2 --enable-libdav1d --enable-libxvid --enable-libzvbi --enable-libzimg
  libavutil      56. 70.100 / 56. 70.100
  libavcodec     58.134.100 / 58.134.100
  libavformat    58. 76.100 / 58. 76.100
  libavdevice    58. 13.100 / 58. 13.100
  libavfilter     7.110.100 /  7.110.100
  libswscale      5.  9.100 /  5.  9.100
  libswresample   3.  9.100 /  3.  9.100
  libpostproc    55.  9.100 / 55.  9.100                                                                                                                                            
Input #0, png_pipe, from 'logo.png':
  Duration: N/A, bitrate: N/A
  Stream #0:0: Video: png, rgba(pc), 601x81 [SAR 2834:2834 DAR 601:81], 25 fps, 25 tbr, 25 tbn, 25 tbc

▶ ffmpeg -i video.mp4                                                                                                   
ffmpeg version 4.4-static https://johnvansickle.com/ffmpeg/  Copyright (c) 2000-2021 the FFmpeg developers
  built with gcc 8 (Debian 8.3.0-6)
  configuration: --enable-gpl --enable-version3 --enable-static --disable-debug --disable-ffplay --disable-indev=sndio --disable-outdev=sndio --cc=gcc --enable-fontconfig --enable-frei0r --enable-gnutls --enable-gmp --enable-libgme --enable-gray --enable-libaom --enable-libfribidi --enable-libass --enable-libvmaf --enable-libfreetype --enable-libmp3lame --enable-libopencore-amrnb --enable-libopencore-amrwb --enable-libopenjpeg --enable-librubberband --enable-libsoxr --enable-libspeex --enable-libsrt --enable-libvorbis --enable-libopus --enable-libtheora --enable-libvidstab --enable-libvo-amrwbenc --enable-libvpx --enable-libwebp --enable-libx264 --enable-libx265 --enable-libxml2 --enable-libdav1d --enable-libxvid --enable-libzvbi --enable-libzimg
  libavutil      56. 70.100 / 56. 70.100
  libavcodec     58.134.100 / 58.134.100
  libavformat    58. 76.100 / 58. 76.100
  libavdevice    58. 13.100 / 58. 13.100
  libavfilter     7.110.100 /  7.110.100
  libswscale      5.  9.100 /  5.  9.100
  libswresample   3.  9.100 /  3.  9.100
  libpostproc    55.  9.100 / 55.  9.100
Input #0, mov,mp4,m4a,3gp,3g2,mj2, from 'video.mp4':
  Metadata:
    major_brand     : isom
    minor_version   : 512
    compatible_brands: isomiso2avc1mp41
    encoder         : Lavf58.76.100
  Duration: 00:00:02.00, start: 0.000000, bitrate: 24 kb/s
  Stream #0:0(und): Video: h264 (High) (avc1 / 0x31637661), yuv420p, 1080x1920, 18 kb/s, 25 fps, 25 tbr, 12800 tbn, 50 tbc (default)
    Metadata:
      handler_name    : VideoHandler
      vendor_id       : [0][0][0][0]


  


• 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.