How to Change the Buffer on VLC

The VLC media player includes file cache and stream buffer options to enable fine-grained control over video playback on machines with limited system resources. If you use VLC to stream network video, you can set the buffer size on a per-stream or permanent basis. For local file playback, you can raise or lower the file cache size to limit the amount of memory VLC uses or the frequency with which it accesses the disk. For systems with low memory, a low cache setting makes more resources available to the operating system.

Permanently Change the Streaming Buffer

  • Click “Tools” and select “Preferences.” In the lower left of the Preferences dialog, select the “All” button under “Show Settings” to display the advanced settings.
  • Select “Stream Output” from the sidebar menu. The setting that affects buffer size is labeled “Stream Output Muxer Caching.”
  • Enter a new amount in milliseconds in the Muxer Caching field. Since this setting requires a value in milliseconds, the amount of memory it uses varies with the streaming video’s quality. If you have ample RAM but a slow network connection, a high setting such as 2,000 ms to 3,000 ms is safe. You may need to experiment to find the right setting for your machine.

Change the Buffer for Individual Streams

  • Press “Ctrl-N” to open a new network stream, then enter a URL in the address field. VLC supports HTTP, FTP, MMS, UDP and RTSP protocols, and you must enter the full URL in the address field.
  • Select “Show More Options” to display advanced settings for the current network stream. The Caching option controls the streaming buffer size.
  • Enter an amount in milliseconds in the Caching field, then click “Play.” Depending on the cache setting, the video may take a few seconds to start streaming.

Change the Buffer for Local Files

  • Click “Tools” and select “Preferences.” In the lower left of the Preferences dialog, select the “All” button under “Show Settings” to display the advanced settings.
  • Select “Input / Codecs” from the sidebar menu, then scroll to the Advanced section in the Input / Codecs panel.
  • Enter a new amount in the File Caching field. The default setting is 300 ms, which results in VLC accessing your disk three times per second. If video playback stutters on your machine, increasing this setting can make it smoother. However, depending on your RAM and CPU resources, you may need to experiment to find the right setting.

Tips & Warnings

  • Information in this article applies to VLC 2.1.5. It may vary slightly or significantly with other versions.


Vendor ID, Product ID information in SIP

As you may know, to be a robust meeting entity, we must take good care of compatibility requirements for different facilities from different manufacturers.

In H.323 protocol, we can use fields like Vendor ID, Product ID, Version ID in the signaling commands.

But how to do this when you are using SIP protocol?

  1. Definitions in RFC 3261

20.35 Server

   The Server header field contains information about the software used

   by the UAS to handle the request.

   Revealing the specific software version of the server might allow the

   server to become more vulnerable to attacks against software that is

   known to contain security holes. Implementers SHOULD make the Server

   header field a configurable option.


      Server: HomeServer v2

20.41 User-Agent

   The User-Agent header field contains information about the UAC

   originating the request.  The semantics of this header field are

   defined in [H14.43].

   Revealing the specific software version of the user agent might allow

   the user agent to become more vulnerable to attacks against software

   that is known to contain security holes.  Implementers SHOULD make

   the User-Agent header field a configurable option.


      User-Agent: Softphone Beta1.5



  1. [H14.43] User-Agent definition in RFC2616

14.43 User-Agent

The User-Agent request-header field contains information about the user agent originating the request. This is for statistical purposes, the tracing of protocol violations, and automated recognition of user agents for the sake of tailoring responses to avoid particular user agent limitations. User agents SHOULD include this field with requests.

The field can contain multiple product tokens (section 3.8) and comments identifying the agent and any subproducts which form a significant part of the user agent. By convention, the product tokens are listed in order of their significance for identifying the application.

User-Agent     = “User-Agent” “:” 1*( product | comment )


User-Agent: CERN-LineMode/2.15 libwww/2.17b3



  1. How TANDBERG and Polycom implemented?

User-Agent format of TANDBERG 775
Server format of TANDBERG 775


User-Agent format of Polycom

So, jump to the conclusion:

  1. As UAC, identify yourself in User-Agent field.
  2. As UAS, identify yourself in Server field.

Comparing with TANDBERG and POLYCOM’s implementation, TANDBERG format is more proper.

Common video communication protocol intro – GB28181

常见视频通信协议介绍 – GB28181
It’s not a world-wide standard, but a Chinese-marketing-only standard, which was drafted by a number of Chinese government facilities.

P.S. It’s a Chinese version of presentation.

Video-communication-protocols-GB28181.ppt[gview file=”Video-communication-protocols-GB28181.pdf” save=”0″]