Merge "MediaFormat: fix javadoc for AAC-related keys" into pi-dev am: 1b3ef3cb

 * <tr><td>{@link #KEY_AAC_DRC_ATTENUATION_FACTOR}</td><td>Integer</td><td><b>decoder-only</b>, optional, if content is AAC audio, specifies the DRC attenuation factor.</td></tr>

 * <tr><td>{@link #KEY_AAC_DRC_HEAVY_COMPRESSION}</td><td>Integer</td><td><b>decoder-only</b>, optional, if content is AAC audio, specifies whether to use heavy compression.</td></tr>

 * <tr><td>{@link #KEY_AAC_MAX_OUTPUT_CHANNEL_COUNT}</td><td>Integer</td><td><b>decoder-only</b>, optional, if content is AAC audio, specifies the maximum number of channels the decoder outputs.</td></tr>

 * <tr><td>{@link #KEY_AAC_DRC_EFFECT_TYPE}</td><td>Integer</td><td><b>decoder-only</b>, optional, if content is AAC audio, specifies the DRC effect type to use.</td></tr>

 * <tr><td>{@link #KEY_AAC_DRC_EFFECT_TYPE}</td><td>Integer</td><td><b>decoder-only</b>, optional, if content is AAC audio, specifies the MPEG-D DRC effect type to use.</td></tr>

 * <tr><td>{@link #KEY_CHANNEL_MASK}</td><td>Integer</td><td>optional, a mask of audio channel assignments</td></tr>

 * <tr><td>{@link #KEY_FLAC_COMPRESSION_LEVEL}</td><td>Integer</td><td><b>encoder-only</b>, optional, if content is FLAC audio, specifies the desired compression level.</td></tr>

 * </table>

     * The gain is derived as the difference between the Target Reference Level and the

     * Program Reference Level. The latter can be given in the bitstream and indicates the actual

     * loudness value of the program item.

     * <p>The Target Reference Level controls loudness normalization for both MPEG-4 DRC and

     * MPEG-D DRC.

     * <p>The value is given as an integer value between

     * 0 and 127, and is calculated as -0.25 * Target Reference Level in dBFS.

     * Therefore, it represents the range of Full Scale (0 dBFS) to -31.75 dBFS.

     * 40 and 127, and is calculated as -4 * Target Reference Level in LKFS.

     * Therefore, it represents the range of -10 to -31.75 LKFS.

     * <p>The default value on mobile devices is 64 (-16 LKFS).

     * <p>This key is only used during decoding.

     */

    public static final String KEY_AAC_DRC_TARGET_REFERENCE_LEVEL = "aac-target-ref-level";

     * clipping<br>

     * The value 6 (General compression) can be used for enabling MPEG-D DRC without particular

     * DRC effect type request.<br>

     * The default is DRC effect type "None".

     * The default DRC effect type is 3 ("Limited playback range") on mobile devices.

     * <p>This key is only used during decoding.

     */

    public static final String KEY_AAC_DRC_EFFECT_TYPE = "aac-drc-effect-type";

    /**

     * A key describing the target reference level that was assumed at the encoder for

     * calculation of attenuation gains for clipping prevention. This information can be provided

     * if it is known, otherwise a worst-case assumption is used.

     * <p>The value is given as an integer value between

     * 0 and 127, and is calculated as -0.25 * Target Reference Level in dBFS.

     * Therefore, it represents the range of Full Scale (0 dBFS) to -31.75 dBFS.

     * The default value is the worst-case assumption of 127.

     * calculation of attenuation gains for clipping prevention.

     * <p>If it is known, this information can be provided as an integer value between

     * 0 and 127, which is calculated as -4 * Encoded Target Level in LKFS.

     * If the Encoded Target Level is unknown, the value can be set to -1.

     * <p>The default value is -1 (unknown).

     * <p>The value is ignored when heavy compression is used (see

     * {@link #KEY_AAC_DRC_HEAVY_COMPRESSION}).

     * <p>This key is only used during decoding.

     * factor is used to enable the negative gains, to prevent loud signal from surprising

     * the listener. In applications which generally need a low dynamic range, both the boost factor

     * and the attenuation factor are used in order to enable all DRC gains.

     * <p>In order to prevent clipping, it is also recommended to apply the attenuation factors

     * <p>In order to prevent clipping, it is also recommended to apply the attenuation gains

     * in case of a downmix and/or loudness normalization to high target reference levels.

     * <p>Both the boost and the attenuation factor parameters are given as integer values

     * between 0 and 127, representing the range of the factor of 0 (i.e. don't apply)

     * to 1 (i.e. fully apply boost/attenuation factors respectively).

     * to 1 (i.e. fully apply boost/attenuation gains respectively).

     * <p>The default value is 127 (fully apply boost DRC gains).

     * <p>This key is only used during decoding.

     */

    public static final String KEY_AAC_DRC_BOOST_FACTOR = "aac-drc-boost-level";

     * actual listening requirements.

     * See {@link #KEY_AAC_DRC_BOOST_FACTOR} for a description of the role of this attenuation

     * factor and the value range.

     * <p>The default value is 127 (fully apply attenuation DRC gains).

     * <p>This key is only used during decoding.

     */

    public static final String KEY_AAC_DRC_ATTENUATION_FACTOR = "aac-drc-cut-level";

     * Light compression usually contains clipping prevention for stereo downmixing while heavy

     * compression, if additionally provided in the bitstream, is usually stronger, and contains

     * clipping prevention for stereo and mono downmixing.

     * <p>The default is light compression.

     * <p>The default is 1 (heavy compression).

     * <p>This key is only used during decoding.

     */

    public static final String KEY_AAC_DRC_HEAVY_COMPRESSION = "aac-drc-heavy-compression";