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• Dreamcast Track Sizes

  1er mars 2015, par Multimedia Mike — Sega Dreamcast

  I’ve been playing around with Sega Dreamcast discs lately. Not playing the games on the DC discs, of course, just studying their structure. To review, the Sega Dreamcast game console used special optical discs named GD-ROMs, where the GD stands for “gigadisc”. They are capable of holding about 1 gigabyte of data.

  You know what’s weird about these discs ? Each one manages to actually store a gigabyte of data. Each disc has a CD portion and a GD portion. The CD portion occupies the first 45000 sectors and can be read in any standard CD drive. This area is divided between a brief data track and a brief (usually) audio track.

  The GD region starts at sector 45000. Sometimes, it’s just one humongous data track that consumes the entire GD region. More often, however, the data track is split between the first track and the last track in the region and there are 1 or more audio tracks in between. But the weird thing is, the GD region is always full. I made a study of it (click for a larger, interactive graph) :

  
  
  

  Some discs put special data or audio bonuses in the CD region for players to discover. But every disc manages to fill out the GD region. I checked up on a lot of those audio tracks that divide the GD data and they’re legitimate music tracks. So what’s the motivation ? Why would the data track be split in 2 pieces like that ?

  I eventually realized that I probably answered this question in this blog post from 4 years ago. The read speed from the outside of an optical disc is higher than the inside of the same disc. When I inspect the outer data tracks of some of these discs, sure enough, there seem to be timing-sensitive multimedia FMV files living on the outer stretches.

  One day, I’ll write a utility to take apart the split ISO-9660 filesystem offset from a weird sector.

• FFmpeg : canvas and crop work separately but result in black screen when combined

  25 janvier, par didi00

  I'm working on a video processing pipeline with FFmpeg, where I :

  


  

  • Create a black canvas using the color filter.

  


  • Crop a region from my video input.

  


  • Overlay the cropped region onto the black canvas.

  


  


  Both the canvas and the crop display correctly when tested individually. However, when I attempt to combine them (overlay the crop onto the canvas), the result is a black screen.
What Works :

  


  Black Canvas Alone :

  


  ffmpeg -filter_complex "color=c=black:s=1920x1080[out]" -map "[out]" -f nut - | ffplay 
-


  


  This shows a plain black screen, as expected.

  


  Cropped Region Alone :

  


  ffmpeg -f v4l2 -input_format yuyv422 -framerate 60 -video_size 1920x1080 -i /dev/video0 
\ -vf "crop=1024:192:0:0" -f nut - | ffplay -


  


  This shows the cropped region of the video correctly.

  


  When I combine these steps to overlay the crop onto the black canvas, I get a black screen :

  


  ffmpeg -f v4l2 -input_format yuyv422 -framerate 60 -video_size 1920x1080 -i /dev/video0 
\-filter_complex "color=c=black:s=1920x1080,format=yuv420p[background]; \
[0:v]crop=1024:192:0:0,format=yuv420p[region0]; \
[background][region0]overlay=x=0:y=0[out]" \
-map "[out]" -f nut - | ffplay -


  


  Environment :

  


  

  • OS : Linux (Debian-based)

  


  • FFmpeg Version : [Insert version, e.g., 4.x or 5.x]

  


  • Capture Card Format : yuyv422

  


  


  Question :

  


  Why does the pipeline result in a black screen when combining the canvas and the crop, even though both work separately ? Is this an issue with pixel format compatibility, or is there something I'm overlooking in the overlay filter setup ?

  


• i am getting when i am trying to run Ffmpegrabberframe on alpine image [closed]

  18 mars 2020, par avinash tiwari

  # # A fatal error has been detected by the Java Runtime Environment :

  # SIGSEGV (0xb) at pc=0x000000000000dc56, pid=446, tid=0x00007fd3c478db20 # # JRE version : OpenJDK Runtime Environment

  (8.0_242-b08) (build 1.8.0_242-b08) # Java VM : OpenJDK 64-Bit Server
  VM (25.242-b08 mixed mode linux-amd64 compressed oops) # Derivative :
  IcedTea 3.15.0 # Distribution : Custom build (Wed Jan 29 10:43:50 UTC
  2020) # Problematic frame : # C 0x000000000000dc56 # # Failed to
  write core dump. Core dumps have been disabled. To enable core
  dumping, try "ulimit -c unlimited" before starting Java again # # An
  error report file with more information is saved as : #
  /builds/had/tip/asset-delivery/firstgen-ingestion---backend/hs_err_pid446.log

  # If you would like to submit a bug report, please include # instructions on how to reproduce the bug and visit : #

  https://icedtea.classpath.org/bugzilla # Exception in thread
  "Thread-8" java.io.EOFException at
  java.io.ObjectInputStream$BlockDataInputStream.peekByte(ObjectInputStream.java:3015)
  at java.io.ObjectInputStream.readObject0(ObjectInputStream.java:1576)
  at java.io.ObjectInputStream.readObject(ObjectInputStream.java:465)
  at java.io.ObjectInputStream.readObject(ObjectInputStream.java:423)
  at
  org.scalatest.tools.Framework$ScalaTestRunner$Skeleton$1$React.react(Framework.scala:818)
  at
  org.scalatest.tools.Framework$ScalaTestRunner$Skeleton$1.run(Framework.scala:807)

  def extractAVI(rawDrivePath: String): List[String] = {
  
      var errorList: List[String] = List.empty
  
      FileUtils.listFiles(new File(rawDrivePath), new SuffixFileFilter(".avi"), TrueFileFilter.INSTANCE)
  
        .asScala.toList.foreach(aviFile => {
  
        var grabber: FFmpegFrameGrabber = null
  
        var aviStream: InputStream = null
  
        var isFailedExtraction: Boolean = false
  
        try {
  
          LOGGER.info(s"--------inside try----------${aviFile.getAbsolutePath}")
  
          aviStream = new FileInputStream(aviFile.getAbsolutePath)
  
          LOGGER.info("--------create grabber----------")
  
          grabber = new FFmpegFrameGrabber(aviStream)
  
          LOGGER.info("--------created grabber extraction of drives----------")
  
          grabber.start()
  
          LOGGER.info("--------start grabber of drives----------")
  
          var count: Int = 1
  
          for (frame <- Iterator.continually(grabber.grabImage()).takeWhile(_ != null)) {
  
            ImageIO.write(converter.convert(frame), "jpg", new File(aviFile.getParent, "capture-" + count + ".jpg"))
  
            count += 1
  
          }
  
          grabber.stop()
  
        } catch {
  
          case ex: Exception => {
  
            LOGGER.info(s"Error while extracting images for ${aviFile.getAbsolutePath} {}", ex)
  
            errorList :+= s"${aviFile.getAbsolutePath.replace(rawDrivePath, "")} -> ${ex.getMessage}"
  
            isFailedExtraction = true
  
            LOGGER.info("last inside catch")
  
          }
  
        } finally {
  
          // Close the video file
  
          LOGGER.info(s"inside finally ")
  
          if (grabber != null)
  
            grabber.release()
  
          if (aviStream != null)
  
            aviStream.close()
  
          if (aviFile.exists() && !isFailedExtraction) {
  
            LOGGER.debug(s"Deleting ${aviFile.getAbsolutePath}")
  
            FileUtils.deleteQuietly(aviFile)
  
          }
  
        }
  
      })