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• MPlayer not playing HTTP video stream for a specific type of content from the same source

  2 août 2017, par Joel

  Implementation overview

  Before I dive into the question, I need to establish the context from the start.

  I am currently implementing a cloud gaming solution utilising the following :

  • Nvidia Capture SDK
  • Nvidia Video Codec SDK
  • FFmpeg
  • MPlayer

  The Nvidia Capture SDK is used to produce a shim layer (via DXGI.dll), intercepting and capturing DirectX frames so that they can be passed to the Nvidia Video Codec SDK to be encoded into an h264 video format. All this is done within DXGI.dll.

  I then pass the encoded video to FFmpeg. FFmpeg acts as an HTTP server that broadcasts the video stream for MPlayer to play.

  Problem

  I am running an Unreal Engine 4 game called "Epic Survival Game Series". The Nvidia Capture SDK’s shim layer kicks off when the game starts, and FFmpeg launches the HTTP server to start streaming. However, when I start MPlayer to receive the stream, MPlayer stops at the following message, and nothing happens after that.

  libavformat version 57.72.101 (internal)
Stream not seekable!
H264-ES file format detected

  The thing is, when I play the same video using ffplay, it works without any issue. This is not the only quirk. When I launch a different Unreal Engine 4 game called "First Person Shooter Template", MPlayer can play that video as well. Also, if I modify the Survival Game to load directly into the game level by skipping the menu, MPlayer is also able to play the video.

  Using FFmpeg to write the video to a file instead of streaming it to a video also works, no matter the game or whether I loaded into the menu or game level.

  This is very strange and I do not have any idea why this is the case. Any ideas ?

  Edit : One strange quirk I forgot to mention is that MPlayer does manage to play the video in very rare occasions - maybe once every 10-20 tries or so.

  Implementation Details

  Additional details of how certain parts are implemented.

  (1) For the Nvidia Capture SDK, I use the provided DXIFRShim example that is provided in the SDK

  (2) for the Nvidia Video Codec SDK, I use the provided NvEncoder example that is provided in the SDK

  (3) The FFmpeg command I use is this :
  ffmpeg -i - -listen 1 -threads 1 -vcodec copy -preset ultrafast -an -tune zerolatency -f h264 http://address:port
  The encoded frames from Nvidia Video Codec SDK is piped to FFmpeg.

  (4) The MPlayer command I use is this :
  mplayer -quiet -vo gl -nosound -benchmark http://address:port

  Things I’ve tried

  I am suspecting MPlayer to be the cause, so I’ve only played around with MPlayer parameters.
  mplayer http://address:port

  mplayer -fps 30 -vo gl -nosound -benchmark http://address:port

  mplayer -fps 30 -screenw 720 -screenh 1280 -vo gl -nosound -benchmark http://address:port

  mplayer -fps 30 -vo directx -nosound -benchmark http://address:port

  mplayer -fps 30 -vo null -nosound -benchmark http://address:port

  None of these worked.

• Revision 37337 : Pas besoin du title qui reprends le titre Une erreur sur un label

  16 avril 2010, par kent1@… — Log

  Pas besoin du title qui reprends le titre
  Une erreur sur un label

• Revisiting Nosefart and Discovering GME

  30 mai 2011, par Multimedia Mike — Game Hacking

  I found the following screenshot buried deep in an old directory structure of mine :

  
  
  

  I tried to recall how this screenshot came to exist. Had I actually created a functional KDE frontend to Nosefart yet neglected to release it ? I think it’s more likely that I used some designer tool (possibly KDevelop) to prototype a frontend. This would have been sometime in 2000.

  However, this screenshot prompted me to revisit Nosefart.

  Nosefart Background
  Nosefart is a program that can play Nintendo Sound Format (NSF) files. NSF files are files containing components that were surgically separated from Nintendo Entertainment System (NES) ROM dumps. These components contain the music playback engines for various games. An NSF player is a stripped down emulation system that can simulate the NES6502 CPU along with the custom hardware (2 square waves, 1 triangle wave, 1 noise generator, and 1 limited digital channel).

  Nosefart was written by Matt Conte and eventually imported into a Sourceforge project, though it has not seen any development since then. The distribution contains standalone command line players for Linux and DOS, a GTK frontend for the Linux command line version, and plugins for Winamp, XMMS, and CL-Amp.

  The Sourceforge project page notes that Nosefart is also part of XBMC. Let the record show that Nosefart is also incorporated into xine (I did that in 2002, I think).

  Upgrading the API
  When I tried running the command line version of Nosefart under Linux, I hit hard against the legacy audio API : OSS. Remember that ?

  In fairly short order, I was able to upgrade the CL program to use PulseAudio. The program is not especially sophisticated. It’s a single-threaded affair which checks for a keypress, processes an audio frame, and sends the frame out to the OSS file interface. All that was needed was to rewrite open_hardware() and close_hardware() for PA and then replace the write statement in play(). The only quirk that stood out is that including <pulse/pulseaudio.h> is insufficient for programming PA’s simple API. <pulse/simple.h> must be included separately.

  For extra credit, I adapted the program to ALSA. The program uses the most simplistic audio output API possible — just keep filling a buffer and sending it out to the DAC.

  Discovering GME
  I’m not sure what to do with the the program now since, during my research to attempt to bring Nosefart up to date, I became aware of a software library named Game Music Emu, or GME. It’s a pure C++ library that can essentially play any classic video game format you can possible name. Wow. A lot can happen in 10 years when you’re not paying attention.

  It’s such a well-written library that I didn’t need any tutorial or documentation to come up to speed. Just a quick read of the main gme.h header library enabled me in short order to whip up a quick C program that could play NSF and SPC files. Path of least resistance : Client program asks library to open a hardcoded file, synthesize 10 seconds of audio, and dump it into a file ; ask the FLAC command line program to transcode raw data to .flac file ; use ffplay to verify the results.

  I might develop some other uses for this library.