Merge "MediaCodec: Fix documentation on float raw audio buffers" into qt-dev

 <h4>Raw Audio Buffers</h4>

 <p>

 Raw audio buffers contain entire frames of PCM audio data, which is one sample for each channel

 in channel order. Each sample is a {@linkplain AudioFormat#ENCODING_PCM_16BIT 16-bit signed

 integer in native byte order}.

 in channel order. Each PCM audio sample is either a 16 bit signed integer or a float,

 in native byte order.

 Raw audio buffers in the float PCM encoding are only possible

 if the MediaFormat's {@linkplain MediaFormat#KEY_PCM_ENCODING}

 is set to {@linkplain AudioFormat#ENCODING_PCM_FLOAT} during MediaCodec

 {@link #configure configure(…)}

 and confirmed by {@link #getOutputFormat} for decoders

 or {@link #getInputFormat} for encoders.

 A sample method to check for float PCM in the MediaFormat is as follows:

 <pre class=prettyprint>

 static boolean isPcmFloat(MediaFormat format) {

   return format.getInteger(MediaFormat.KEY_PCM_ENCODING, AudioFormat.ENCODING_PCM_16BIT)

       == AudioFormat.ENCODING_PCM_FLOAT;

 }</pre>

 In order to extract, in a short array,

 one channel of a buffer containing 16 bit signed integer audio data,

 the following code may be used:

 <pre class=prettyprint>

 // Assumes the buffer PCM encoding is 16 bit.

 short[] getSamplesForChannel(MediaCodec codec, int bufferId, int channelIx) {

   ByteBuffer outputBuffer = codec.getOutputBuffer(bufferId);

   MediaFormat format = codec.getOutputFormat(bufferId);

   ShortBuffer samples = outputBuffer.order(ByteOrder.nativeOrder()).asShortBuffer();

   int numChannels = formet.getInteger(MediaFormat.KEY_CHANNEL_COUNT);

   int numChannels = format.getInteger(MediaFormat.KEY_CHANNEL_COUNT);

   if (channelIx < 0 || channelIx >= numChannels) {

     return null;

   }