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• Cortex-A7 instruction cycle timings

  15 mai 2014, par Mans — ARM

  The Cortex-A7 ARM core is a popular choice in low-power and low-cost designs. Unfortunately, the public TRM does not include instruction timing information. It does reveal that execution is in-order which makes measuring the throughput and latency for individual instructions relatively straight-forward. The table below lists the measured issue cycles … Continue reading →

• Capture raw video byte stream for real time transcoding

  9 septembre 2012, par user1145905

  I would like to achieve the following :

  Set up a proxy server to handle video requests by clients (for now, say all video requests from any Android video client) from a remote video server like YouTube, Vimeo, etc. I don't have access to the video files being requested, hence the need for a proxy server. I have settled for Squid. This proxy should process the video signal/stream being passed from the remote server before relaying it back to the requesting client.

  To achieve the above, I would either

  1. Need to figure out the precise location (URL) of the video resource being requested, download it really fast, and modify it as I want before HTTP streaming it back to the client as the transcoding continues (simultaneously, with some latency)

  2. Access the raw byte stream, pipe it into a transcoder (I'm thinking ffmpeg) and proceed with the streaming to client (also with some expected latency).

  Option #2 seems tricky to do but lends more flexibility to the kind of transcoding I would like to perform. I would have to actually handle raw data/packets, but I don't know if ffmpeg takes such input.

  In short, I'm looking for a solution to implement real-time transcoding of videos that I do not have direct access to from my proxy. Any suggestions on the tools or approaches I could use ? I have also read about Gstreamer (but could not tell if it's applicable to my situation), and MPlayer/MEncoder.

  And finally, a rather specific question : Are there any tools out there that, given a YouTube video URL, can download the byte stream for further processing ? That is, something similar to the Chrome YouTube downloader but one that can be integrated with a server-side script ?

  Thanks for any pointers/suggestions !

• MP4 libx264 converted to libx265 results in skipped frames

  5 mai 2023, par RGC

  FFmpeg 5-1-2-full_build on Windows10 and storage on windows server 2016.
We have about 1.5 TB data in videos as evidence to document compliance to manufacturing standards.
In a PowerShell batch script I move an libx264 mp4 to a USB3 backup location and then convert it back to the server location it came from :
FFMpeg -i backup\inputFile.mp4 c:v libx265 \server\outputFile.mp4 -n
in order to save much needed space on our server.
It did create a significantly smaller file, but while reviewing the results the length in time is the same as the input but frames seems like they were dropped.

  


  I am stumped as to use what additional parameters as ffmpeg has so many.
Can the fact that it does the conversion over a network to the server be an influence, or the input coming from a USB3 backup drive ?

  


  Thanks for your feedback,
RGC

  


  $noOfFiles++                            # count progress   
$serverMp4 = "$serverLine"          # Server MP4 input address

# Before Conversion grab MP4 from server and move to backup drive
# First grab input file path name and add as destination path, if not exist
$backupMp4 = $serverMp4.Substring(2)
$backupMp4 = "E:\Videos$backupMp4"
$serverLastFolder = (Split-Path $serverLine -Parent)
$serverLastFolder = (Split-Path $serverLastFolder -NoQualifier)
$destinationPath = Join-Path $destinationFolder $serverLastFolder
if(!(Test-Path $destinationPath)) {
    New-Item -ItemType Directory -Path $destinationPath
}

Move-Item -Path $serverMp4 -Destination $destinationPath

$myTime = get-date -format "yyyy-MM-dd HH:mm:ss"        # log Move
$msgOut = "$myTime Moved $serverMp4  to E:\Videos\"
Add-Content -Path $log -Value $msgOut        # store msg in log file
Write-Host $msgOut

# Convert file back to server
ffmpeg -i  $backupMp4 -c:v libx265 $serverMp4 -n

$myTime = get-date -format "yyyy-MM-dd HH:mm:ss"
$msgOut = "$myTime Converted $backupMp4 `n $arrow      $serverMp4"
Write-Host $msgOut                           # Console msg
Add-Content -Path $log -Value $msgOut        # store msg in log file

Write-Host "Completed Move of: $noOfFiles `n $sepLine" -ForegroundColor DarkYellow

# Finished Move of MP4 file to Backup Drive and Converted back to original location. 
# Grab next line  


  


  }