Q: Mini DisplayPort to HDTV Cable

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Only some computers support audio over Mini DisplayPort > http://support.apple.com/kb/HT4241

The Mid 2010 MacBook Pro includes audio compatibility over Mini DisplayPort, so as you have a Mid 2009 MacBook Pro, it's normal that you do not get sound. You have to look for external speakers or another way to use your TV as the output sound device

That is becaise a 2009 MBP does not support sound through the minidisplay port.  You will have to tap the audio output port for sound via a 'Y' cable with RCA connectors.

Ciao.

The problem is that Mini DisplayPort doesn't support audio in your Mac, so you can't use any peripheral for audio and video that use this port. Audio and video have to be transferred to an external display or peripheral separately

Video will be transmitted via the minidisplay to HDMI port on the television which you already have.  For audio you will need something on the order of this:

http://www.bhphotovideo.com/bnh/controller/home?O=&sku=160638&Q=&is=REG&A=detail s

There is NO single cable option available for a 2009 MBP.

Ciao.