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I am trying to determine the format of the audio portion of a video being sent from a digital device (DVD player, DVR, etc.) to a digital TV via an HDMI cable. My understanding is that the audio portion of this video is converted to a standard uncompressed PCM format. Is this correct?

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Not necessarily. HDMI devices supporting audio transmission MUST support 2-channel L-PCM but there are a variety of other optional audio formats allowed by the HDMI 1.4b specification.

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Ok, but the bottom line is that all HDMI devices MUST support LPCM, correct? thanks! – Bcorngtr Mar 1 '12 at 3:57
@Bcorngtr, yes, if the device supports any audio formats, LPCM must be one of them. – Mike Fitzpatrick Mar 1 '12 at 5:18

It must support uncompressed PCM, yes

Audio data, which can consist of any compressed, non-compressed, PCM, single or multi-channel formats (including the new DTS-HD Master Audio and Dolby TrueHD formats for blue laser DVDs), fit into the video blanking intervals and are sent as HDMI packets.

source page 10

For digital audio, if an HDMI device supports audio, it is required to support the baseline format: stereo (uncompressed) PCM. Other formats are optional, with HDMI allowing up to 8 channels of uncompressed audio at sample sizes of 16-bit, 20-bit and 24-bit, with sample rates of 32 kHz, 44.1 kHz, 48 kHz, 88.2 kHz, 96 kHz, 176.4 kHz and 192 kHz.

from wikipedia

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