Is Output Buffering Causing My Web Camera Feed to Freeze?

How to Disable Output Buffering in PHP

The Problem

When streaming data from a web camera using PHP's print function, some buffering seems to occur. At low frame rates, the feed freezes and then displays multiple frames rapidly. This issue is suspected to result from the output buffer.

The Solution

Step 1: Disable output buffering

• Globally, by disabling output_buffering in php.ini or Apache config:

  php_flag "output_buffering" Off

• For the specific script, call either ob_end_flush() or ob_end_clean().

Step 2: Disable server-level output buffering

• Call ob_implicit_flush() at the start of the script.
• Call flush() after every output-producing statement.

Explanation

PHP employs two layers of buffering: the output buffer and the write buffer/server buffer.

Output Buffer

• Controlled by ob_start(), ob_end_flush(), and ob_end_clean().
• Buffers output to the response body.
• Default limit is 4096 bytes.
• Disable globally by setting output_buffering to Off or locally by calling ob_end_clean()/ob_end_flush().

Write Buffer and Server Buffer

• Controlled by flush().
• Buffers output from PHP and the backend (web server or CGI).
• May be influenced by the web server's buffering scheme.
• Enable implicit flushing by calling ob_implicit_flush() or setting implicit_flush to On in php.ini (not recommended due to potential performance implications).

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