NalUnitUtil (ExoPlayer library)

java.lang.Object
- com.google.android.exoplayer2.util.NalUnitUtil

```
public final class NalUnitUtil
extends Object
```
Utility methods for handling H.264/AVC and H.265/HEVC NAL units.

Nested Class Summary

Nested Classes
Modifier and Type	Class	Description
`static class`	`NalUnitUtil.PpsData`	Holds data parsed from a picture parameter set NAL unit.
`static class`	`NalUnitUtil.SpsData`	Holds data parsed from a sequence parameter set NAL unit.

Field Summary

Fields
Modifier and Type	Field	Description
`static float[]`	`ASPECT_RATIO_IDC_VALUES`	Aspect ratios indexed by aspect_ratio_idc, in H.264 and H.265 SPSs.
`static int`	`EXTENDED_SAR`	Value for aspect_ratio_idc indicating an extended aspect ratio, in H.264 and H.265 SPSs.
`static byte[]`	`NAL_START_CODE`	Four initial bytes that must prefix NAL units for decoding.

Method Summary

All Methods Static Methods Concrete Methods
Modifier and Type	Method	Description
`static void`	`clearPrefixFlags(boolean[] prefixFlags)`	Clears prefix flags, as used by `findNalUnit(byte[], int, int, boolean[])`.
`static void`	`discardToSps(ByteBuffer data)`	Discards data from the buffer up to the first SPS, where `data.position()` is interpreted as the length of the buffer.
`static int`	`findNalUnit(byte[] data, int startOffset, int endOffset, boolean[] prefixFlags)`	Finds the first NAL unit in `data`.
`static int`	`getH265NalUnitType(byte[] data, int offset)`	Returns the type of the H.265 NAL unit in `data` that starts at `offset`.
`static int`	`getNalUnitType(byte[] data, int offset)`	Returns the type of the NAL unit in `data` that starts at `offset`.
`static boolean`	`isNalUnitSei(String mimeType, byte nalUnitHeaderFirstByte)`	Returns whether the NAL unit with the specified header contains supplemental enhancement information.
`static NalUnitUtil.PpsData`	`parsePpsNalUnit(byte[] nalData, int nalOffset, int nalLimit)`	Parses a PPS NAL unit using the syntax defined in ITU-T Recommendation H.264 (2013) subsection 7.3.2.2.
`static NalUnitUtil.SpsData`	`parseSpsNalUnit(byte[] nalData, int nalOffset, int nalLimit)`	Parses an SPS NAL unit using the syntax defined in ITU-T Recommendation H.264 (2013) subsection 7.3.2.1.1.
`static int`	`unescapeStream(byte[] data, int limit)`	Unescapes `data` up to the specified limit, replacing occurrences of [0, 0, 3] with [0, 0].

Methods inherited from class java.lang.Object
clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

- Field Detail
  - NAL_START_CODE
```
public static final byte[] NAL_START_CODE
```
    Four initial bytes that must prefix NAL units for decoding.
  - EXTENDED_SAR
```
public static final int EXTENDED_SAR
```
    Value for aspect_ratio_idc indicating an extended aspect ratio, in H.264 and H.265 SPSs.
    
    See Also:
    
    Constant Field Values
  - ASPECT_RATIO_IDC_VALUES
```
public static final float[] ASPECT_RATIO_IDC_VALUES
```
    Aspect ratios indexed by aspect_ratio_idc, in H.264 and H.265 SPSs.
- Method Detail
  - unescapeStream
```
public static int unescapeStream(byte[] data,
                                 int limit)
```
    Unescapes data up to the specified limit, replacing occurrences of [0, 0, 3] with [0, 0]. The unescaped data is returned in-place, with the return value indicating its length.
    Executions of this method are mutually exclusive, so it should not be called with very large buffers.
    
    Parameters:
    
    data - The data to unescape.
    
    limit - The limit (exclusive) of the data to unescape.
    
    Returns:
    
    The length of the unescaped data.
  - discardToSps
```
public static void discardToSps(ByteBuffer data)
```
    Discards data from the buffer up to the first SPS, where data.position() is interpreted as the length of the buffer.
    When the method returns, data.position() will contain the new length of the buffer. If the buffer is not empty it is guaranteed to start with an SPS.
    
    Parameters:
    
    data - Buffer containing start code delimited NAL units.
  - isNalUnitSei
```
public static boolean isNalUnitSei(@Nullable
                                   String mimeType,
                                   byte nalUnitHeaderFirstByte)
```
    Returns whether the NAL unit with the specified header contains supplemental enhancement information.
    
    Parameters:
    
    mimeType - The sample MIME type, or null if unknown.
    
    nalUnitHeaderFirstByte - The first byte of nal_unit().
    
    Returns:
    
    Whether the NAL unit with the specified header is an SEI NAL unit. False is returned if the MimeType is null.
  - getNalUnitType
```
public static int getNalUnitType(byte[] data,
                                 int offset)
```
    Returns the type of the NAL unit in data that starts at offset.
    
    Parameters:
    
    data - The data to search.
    
    offset - The start offset of a NAL unit. Must lie between -3 (inclusive) and data.length - 3 (exclusive).
    
    Returns:
    
    The type of the unit.
  - getH265NalUnitType
```
public static int getH265NalUnitType(byte[] data,
                                     int offset)
```
    Returns the type of the H.265 NAL unit in data that starts at offset.
    
    Parameters:
    
    data - The data to search.
    
    offset - The start offset of a NAL unit. Must lie between -3 (inclusive) and data.length - 3 (exclusive).
    
    Returns:
    
    The type of the unit.
  - parseSpsNalUnit
```
public static NalUnitUtil.SpsData parseSpsNalUnit(byte[] nalData,
                                                  int nalOffset,
                                                  int nalLimit)
```
    Parses an SPS NAL unit using the syntax defined in ITU-T Recommendation H.264 (2013) subsection 7.3.2.1.1.
    
    Parameters:
    
    nalData - A buffer containing escaped SPS data.
    
    nalOffset - The offset of the NAL unit header in nalData.
    
    nalLimit - The limit of the NAL unit in nalData.
    
    Returns:
    
    A parsed representation of the SPS data.
  - parsePpsNalUnit
```
public static NalUnitUtil.PpsData parsePpsNalUnit(byte[] nalData,
                                                  int nalOffset,
                                                  int nalLimit)
```
    Parses a PPS NAL unit using the syntax defined in ITU-T Recommendation H.264 (2013) subsection 7.3.2.2.
    
    Parameters:
    
    nalData - A buffer containing escaped PPS data.
    
    nalOffset - The offset of the NAL unit header in nalData.
    
    nalLimit - The limit of the NAL unit in nalData.
    
    Returns:
    
    A parsed representation of the PPS data.
  - findNalUnit
```
public static int findNalUnit(byte[] data,
                              int startOffset,
                              int endOffset,
                              boolean[] prefixFlags)
```
    Finds the first NAL unit in data.
    If prefixFlags is null then the first three bytes of a NAL unit must be entirely contained within the part of the array being searched in order for it to be found.
    When prefixFlags is non-null, this method supports finding NAL units whose first four bytes span data arrays passed to successive calls. To use this feature, pass the same prefixFlags parameter to successive calls. State maintained in this parameter enables the detection of such NAL units. Note that when using this feature, the return value may be 3, 2 or 1 less than startOffset, to indicate a NAL unit starting 3, 2 or 1 bytes before the first byte in the current array.
    
    Parameters:
    
    data - The data to search.
    
    startOffset - The offset (inclusive) in the data to start the search.
    
    endOffset - The offset (exclusive) in the data to end the search.
    
    prefixFlags - A boolean array whose first three elements are used to store the state required to detect NAL units where the NAL unit prefix spans array boundaries. The array must be at least 3 elements long.
    
    Returns:
    
    The offset of the NAL unit, or endOffset if a NAL unit was not found.
  - clearPrefixFlags
```
public static void clearPrefixFlags(boolean[] prefixFlags)
```
    Clears prefix flags, as used by findNalUnit(byte[], int, int, boolean[]).
    
    Parameters:
    
    prefixFlags - The flags to clear.

Class NalUnitUtil

Nested Class Summary

Field Summary

Method Summary

Methods inherited from class java.lang.Object

Field Detail

NAL_START_CODE

EXTENDED_SAR

ASPECT_RATIO_IDC_VALUES

Method Detail

unescapeStream

discardToSps

isNalUnitSei

getNalUnitType

getH265NalUnitType

parseSpsNalUnit

parsePpsNalUnit

findNalUnit

clearPrefixFlags