requestContentType

Indicates the format for audio input or that the content is text. The header must start with one of the following prefixes:

• PCM format, audio data must be in little-endian byte order.

• audio/l16; rate=16000; channels=1

• audio/x-l16; sample-rate=16000; channel-count=1

• audio/lpcm; sample-rate=8000; sample-size-bits=16; channel-count=1; is-big-endian=false

• Opus format

• audio/x-cbr-opus-with-preamble;preamble-size=0;bit-rate=256000;frame-size-milliseconds=4

• Text format

• text/plain; charset=utf-8