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// Copyright 2018 The Fuchsia Authors. All rights reserved.
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.
library fuchsia.media;
using fuchsia.sysmem;
const uint32 MAX_KEY_ID_SIZE = 16;
const uint32 MAX_INIT_VECTOR_SIZE = 16;
const uint32 MAX_ENCRYPTION_SCHEME_SIZE = 100;
/// Value
///
/// Generic "value" for use within generic "Parameter" struct.
union Value {
1: bool bool_value;
2: uint64 uint64_value;
3: int64 int64_value;
4: string string_value;
// Prefer using oob_bytes instead.
5: bytes bytes_value;
};
/// Parameter
///
/// Generic parameter.
///
/// We want to minimize use of this generic "Parameter" structure by natively
/// defining as many stream-specific parameter semantics as we can.
///
// TODO: When possible, describe the very limited scenarios in which it would
// still be reasonable to use a generic Parameter.
struct Parameter {
// Some indication of the scope of applicability of this Parameter.
string scope;
// Specific name of this parameter, without the scope prefix.
string name;
// The particular value of this parameter.
Value value;
};
/// StreamError
///
/// This error code encapsulates various errors that might emanate from a
/// StreamProcessor server. It can be sent either as an OnStreamFailed event or
/// as an epitaph for the channel.
enum StreamError : uint32 {
// Common errors 0x00
/// An internal error with an unspecified reason.
UNKNOWN = 0x00000001;
/// The client provided invalid input format details.
INVALID_INPUT_FORMAT_DETAILS = 0x00000002;
/// The server received buffers that are not suitable for the operation to
/// be performed. An example of this would be if a Decoder received output
/// buffers that are too small to decode a frame into.
INCOMPATIBLE_BUFFERS_PROVIDED = 0x00000003;
/// Processing of input EOS (end of stream) failed, so the stream failed.
/// Currently this can occur if a core codec watchdog fires while processing
/// EOS.
EOS_PROCESSING = 0x00000004;
// Decoder errors 0x01
/// An internal decoder error with an unspecified reason.
DECODER_UNKNOWN = 0x01000001;
/// Input data that can't be parsed. Only some parsing problems/errors are
/// reported this way. Corrupt input data may be reported as other
/// StreamError, or may not cause a StreamError.
DECODER_DATA_PARSING = 0x01000002;
// Encoder errors 0x02
/// An internal encoder error with an unspecified reason.
ENCODER_UNKNOWN = 0x02000001;
// Decryptor errors 0x03
/// An internal decryptor error with an unspecified reason.
DECRYPTOR_UNKNOWN = 0x03000001;
/// The requested KeyId is not available for use by the Decryptor. The
/// client may try again later if that key becomes available.
DECRYPTOR_NO_KEY = 0x03000002;
};
flexible union AudioCompressedFormat {
1: AudioCompressedFormatAac aac;
2: AudioCompressedFormatSbc sbc;
};
enum AudioBitrateMode {
// Used mainly when a client is configuring an encoder's output format. May
// also be present in an OnOutputConstraints() message from an encoder, but
// should not be relied upon to be present by any consumer downstream of an
// encoder.
UNSPECIFIED = 0;
CBR = 1;
VBR = 2;
};
struct AudioCompressedFormatAac {
};
struct AudioCompressedFormatSbc {
};
/// AudioPcmMode
///
// TODO(dustingreen): Keep or discard any non-linear formats for purposes of the
// Codec interface?
enum AudioPcmMode {
// 16 bit signed int linear or 32 bit float linear, for now
// 1-N channels ok, with "A.B" channels designated as A+B channel_count -
// the channel map is separately specified. So 5.1 becomes channel_count 6.
LINEAR = 0;
// G.711 8 bit format-defined waveform semantics
// 1 channel
ALAW = 1;
// G.711 8 bit format-defined waveform semantics
// 1 channel
MULAW = 2;
};
/// AudioChannelId
///
/// Used in specifying which audio channel is for which speaker location / type.
///
/// TODO(dustingreen): Do we need more channel IDs than this?
///
// TODO(dustingreen): Check with mpuryear@ re. naming consistency for "S" vs.
// "R" as we move these to a common definition. Also the ordering of LS/RS vs.
// LR/RR - probably LR/RR being first would make more sense re. how channels
// get added incrementally, but changing the order would no longer match
// Android's ordering.
enum AudioChannelId {
SKIP = 0; // unused channel
LF = 1; // left front
RF = 2; // right front
CF = 3; // center front
LS = 4; // left surround
RS = 5; // right surround
LFE = 6; // low frequency effects
CS = 7; // back surround
LR = 8; // left rear
RR = 9; // right rear
// This is the last explicitly-defined value + 1. This name will be
// re-defined in future if we add more defined channel IDs above.
END_DEFINED = 10;
// This is where format-specific (or ad-hoc) channel ID values should go, to
// avoid colliding with any additional values allocated above. The values
// here are not guaranteed to avoid collision across different formats.
EXTENDED_CHANNEL_ID_BASE = 0x6f000000;
// Extended channel IDs should be <= Max.
MAX = 0x7fffffff;
};
/// PcmFormat
///
/// PCM audio format details.
///
// TODO(dustingreen): Discuss with mpuryear@ re. where definitions for these
// details go and make sure the common details can specify at least this much.
struct PcmFormat {
// Implicit details:
// * For bits_per_sample > 8, host-endian is implied.
// * At least for now, for channel_count >= 2, interleaved layout is
// implied.
AudioPcmMode pcm_mode;
// bits_per_sample
//
// A "sample" is for a single channel.
//
// For example, CD quality is 16. See PcmMode comments, as the mode
// constrains this value.
uint32 bits_per_sample;
// frames_per_second
//
// A "frame" is one datapoint (one "sample") for each channel. Each channel
// is sampled this many times per second. For example, CD quality is 44100.
uint32 frames_per_second;
// channel_map
//
// channel_map.size() is the channel count. See PcmMode comments, as some
// modes constrain the channel count to 1.
//
// Values from AudioChannelId should be used if they are suitable.
//
// If a channel has no suitable AudioChannelId, an ad-hoc value can be used
// in a range starting from AudioChannel_ExtendedChannelIdBase.
vector<AudioChannelId>:16 channel_map;
// TODO(dustingreen): Add unsigned 8 bit, float 32 bit, maybe others. FWIW,
// AOSP appears to support signed 16 bit, unsigned 8 bit, and float 32 bit
// under "Pcm", AFAICT based on OMX_NUMERICALDATATYPE and ACodec.cpp code.
};
/// AudioUncompressedFormat
///
// Uncompressed audio format details.
union AudioUncompressedFormat {
1: PcmFormat pcm;
};
/// AudioFormat
///
// Audio format details.
union AudioFormat {
1: AudioCompressedFormat compressed;
2: AudioUncompressedFormat uncompressed;
};
/// VideoCompressedFormat
///
/// Compressed video format details.
///
// If a compressed video format has no fields here, it's because it's a good
// format and is already self-describing given the mime_type + format-defined
// oob_bytes as appropriate + in-band data.
union VideoCompressedFormat {
// TODO(dustingreen): Any compressed video formats that aren't sufficiently
// self-describing to select and create a Codec instance to decode it?
// TODO(dustingreen): temp field to make the compiler happy until we have at
// least one real field.
1: uint32 temp_field_todo_remove;
};
enum VideoColorSpace {
// TODO(dustingreen): add to this list
INVALID = 0;
};
/// VideoUncompressedFormat
///
/// Uncompressed video format details.
///
// TODO(dustingreen): Integrate with a system-wide structure for this purpose.
// In progress - see image_format field below which will take the place of this
// struct/table.
struct VideoUncompressedFormat {
// TODO(dustingreen): This will replace VideoUncompressedFormat (after
// struct to table change merges).
fuchsia.sysmem.ImageFormat_2 image_format;
// fourcc
//
// A human-readable fourcc like RGBA should be 0x41424752 in the fourcc
// field (regardless of host endian-ness). Note that the R (first character)
// of the fourcc is in the low-order byte of this fourcc field.
//
// There are some fourcc codes that don't format nicely as a string. While
// I don't foresee any use of any of the purely numeric fourcc codes (not
// corresponding to packed ascii character values), those would be stored
// such that their numeric value has it's low-order byte in the low-order
// byte of this fourcc value. So a fourcc with "hex value" 0x00000001 would
// have the numeric value 1 in this field.
//
// The endian-ness of fourcc values stored in files or in network packets is
// outside the scope of these comments, other than to state that regardless
// of the source of the fourcc code and the order that storage /
// transmission format stores these bytes, a human-readable fourcc should
// have its human-read first ascii character value in the low order byte of
// this field.
uint32 fourcc;
// For formats with different planes having different resolution, this is
// the resolution of the highest-resolution plane(s). Else it's the
// resolution of all the planes.
uint32 primary_width_pixels;
uint32 primary_height_pixels;
// For formats where the secondary planes are the same resolution, these
// fields will be the same as primary_width_pixels and
// primary_height_pixels. For formats with smaller secondary resolutions,
// these indicate that resolution.
uint32 secondary_width_pixels;
uint32 secondary_height_pixels;
// Planar means the various planes are separately stored in their own chunks
// of memory.
bool planar;
// If a format is swizzled, the swizzling parameters are not directly here.
bool swizzled;
uint32 primary_line_stride_bytes;
// Formats with the same stride for all planes will have this field equal to
// primary_line_stride_bytes.
uint32 secondary_line_stride_bytes;
// R or Y
uint32 primary_start_offset;
// G or U
uint32 secondary_start_offset;
// B or V
uint32 tertiary_start_offset;
uint32 primary_pixel_stride;
// For formats with the same pixel stride for all planes, this field will be
// equal to primary_pixel_stride.
uint32 secondary_pixel_stride;
// These override the primary_width_pixels and primary_height_pixels for
// purposes of display (but not for purposes of determining the pixel layout
// in memory). These can crop on the right and bottom. These must be <=
// the corresponding coded dimension.
//
// This value must be <= primary_width_pixels.
uint32 primary_display_width_pixels;
// This value must be <= primary_height_pixels.
uint32 primary_display_height_pixels;
// The pixel_aspect_ratio_width : pixel_aspect_ratio_height is the pixel
// aspect ratio (AKA sample aspect ratio aka SAR) for the luma (AKA Y)
// samples. A pixel_aspect_ratio of 1:1 mean square pixels. A
// pixel_aspect_ratio of 2:1 would mean pixels that are displayed twice as
// wide as they are tall. Codec implementation should ensure these two
// values are relatively prime by reducing the fraction (dividing both by
// GCF) if necessary.
//
// When has_pixel_aspect_ratio == false, pixel_aspect_ratio_width and
// pixel_aspect_ratio_height will both be 1, but in that case the
// pixel_aspect_ratio_width : pixel_aspect_ratio_height of 1:1 is just a
// very weak suggestion re. reasonable-ish handling, not in any way
// authoritative. In this case (or in any case really) the receiver of this
// message may have other OOB means to determine the actual
// pixel_aspect_ratio.
bool has_pixel_aspect_ratio = false;
uint32 pixel_aspect_ratio_width = 1;
uint32 pixel_aspect_ratio_height = 1;
};
/// VideoFormat
///
/// Video (compress or uncompressed) format details. In this context,
/// "uncompressed" can include block-based image compression formats that still
/// permit fairly fast random access to image data.
union VideoFormat {
1: VideoCompressedFormat compressed;
2: VideoUncompressedFormat uncompressed;
};
// Encryption schemes as defined by ISO 23001-7: Common encryption in ISO base
// media file format files. These are defined as strings rather than enums so as
// to not limit the encryption schemes that an implementation supports to the
// constants that are defined here.
using EncryptionScheme = string:MAX_ENCRYPTION_SCHEME_SIZE;
const string ENCRYPTION_SCHEME_UNENCRYPTED = "unencrypted";
const string ENCRYPTION_SCHEME_CENC = "cenc";
const string ENCRYPTION_SCHEME_CBC1 = "cbc1";
const string ENCRYPTION_SCHEME_CENS = "cens";
const string ENCRYPTION_SCHEME_CBCS = "cbcs";
using KeyId = bytes:MAX_KEY_ID_SIZE;
using InitVector = bytes:MAX_INIT_VECTOR_SIZE;
/// SubsampleEntry
///
/// A subsample is a byte range within a sample consisting of a clear byte range
/// followed by an encrypted byte range. This structure specifies the size of
/// each range in the subsample.
struct SubsampleEntry {
uint32 clear_bytes;
uint32 encrypted_bytes;
};
/// EncryptionPattern
///
/// Pattern encryption utilizes a pattern of encrypted and clear 16 byte blocks
/// over the protected range of a subsample (the encrypted_bytes of a
/// `SubsampleEntry`). This structure specifies the number of encrypted data
/// blocks followed by the number of clear data blocks.
struct EncryptionPattern {
uint32 clear_blocks;
uint32 encrypted_blocks;
};
/// EncryptedFormat
///
/// The stream format details payload of a decrypting stream processor. This is
/// a sparsely populated table to specify parameters necessary for decryption
/// other than the data stream. It is only necessary to update fields if they
/// changed, but not an error if the same value is repeated.
table EncryptedFormat {
1: reserved;
2: reserved;
7: reserved;
/// `scheme` specifies which encryption scheme to use, such as
/// `fuchsia.media.ENCRYPTION_SCHEME_CENC`.
/// Usage:
/// - It is required to be set prior to delivery of input packets.
/// - Changing the scheme mid-stream is only permitted in some scenarios.
/// Once an encrypted scheme is selected for a stream, the scheme may
/// only be set to `fuchsia.media.ENCRYPTION_SCHEME_UNENCRYPTED` or that
/// same initial encrypted scheme. The scheme may be set to
/// `fuchsia.media.ENCRYPTION_SCHEME_UNENCRYPTED` at any point.
6: string scheme;
/// `key_id` identifies the key that should be used for decrypting
/// subsequent data.
/// Usage:
/// - It is required to be set prior to delivery of input packets to a
/// decryptor.
/// - This may be changed multiple times during a data stream.
8: KeyId key_id;
/// `init_vector` is used in combination with a key and a block of content
/// to create the first cipher block in a chain and derive subsequent cipher
/// blocks in a cipher block chain.
/// Usage:
/// - It is required to be set prior to the delivery of input packets to a
/// decryptor.
/// - This may be changed multiple times during a data stream.
3: InitVector init_vector;
/// `subsamples` is used to identify the clear and encrypted portions of a
/// subsample.
/// Usage:
/// - For whole sample encryption, this parameter should not be sent.
/// - This may be changed multiple times during a data stream.
4: vector<SubsampleEntry> subsamples;
/// `pattern` is used to identify the clear and encrypted blocks for pattern
/// based encryption.
/// Usage:
/// - This is not allowed for CENC and CBC1 and required for CENS and CBCS.
/// - If required, it must be set prior to the delivery of input packets to
/// a decryptor.
/// - This may be changed multiple times during a data stream.
5: EncryptionPattern pattern;
};
/// DecryptedFormat
///
/// This describes the format of the decrypted content. It is required to be
/// sent by the StreamProcessor server prior to the delivery of output packets.
/// Currently, there is no additional format details for decrypted output.
table DecryptedFormat {
// TODO(FIDL-709): Empty tables cause dart analysis error. Remove this
// unused field once the issue is resolved.
1: bool ignore_this_field;
};
/// CryptoFormat
///
/// Crypto (encrypted or decrypted) format details.
flexible union CryptoFormat {
1: EncryptedFormat encrypted;
2: DecryptedFormat decrypted;
};
/// DomainFormat
///
// Domain-specific format details (audio or video, compressed or uncompressed).
union DomainFormat {
1: AudioFormat audio;
2: VideoFormat video;
3: CryptoFormat crypto;
};
const uint64 kMaxOobBytesSize = 8192;
enum SbcSubBands {
SUB_BANDS_4 = 4;
SUB_BANDS_8 = 8;
};
enum SbcBlockCount {
BLOCK_COUNT_4 = 4;
BLOCK_COUNT_8 = 8;
BLOCK_COUNT_12 = 12;
BLOCK_COUNT_16 = 16;
};
enum SbcAllocation {
ALLOC_LOUDNESS = 0;
ALLOC_SNR = 1;
};
enum SbcChannelMode {
MONO = 0;
DUAL = 1;
STEREO = 2;
JOINT_STEREO = 3;
};
/// Settings for an SBC Encoder.
///
/// SBC Encoders take signed little endian 16 bit linear PCM samples and
/// return encoded SBC frames. SBC encoder PCM data in batches of
/// `sub_bands * block_count` PCM frames. This encoder will accept PCM data on
/// arbitrary frame boundaries, but the output flushed when EOS is queued may be
/// zero-padded to make a full batch for encoding.
struct SbcEncoderSettings {
SbcSubBands sub_bands = SbcSubBands.SUB_BANDS_8;
SbcAllocation allocation = SbcAllocation.ALLOC_LOUDNESS;
SbcBlockCount block_count = SbcBlockCount.BLOCK_COUNT_4;
SbcChannelMode channel_mode;
/// SBC bit pool value.
uint64 bit_pool;
};
/// Raw AAC access units.
struct AacTransportRaw {
};
/// AAC inside LATM
struct AacTransportLatm {
/// Whether MuxConfiguration stream element is present
bool mux_config_present;
};
/// AAC inside ADTS
struct AacTransportAdts {
};
flexible union AacTransport {
1: AacTransportRaw raw;
2: AacTransportLatm latm;
3: AacTransportAdts adts;
};
enum AacChannelMode {
MONO = 0;
STEREO = 2;
};
struct AacConstantBitRate {
/// Bits per second
uint32 bit_rate;
};
/// Variable bit rate modes. The actual resulting bitrate
/// varies based on input signal and other encoding settings.
///
/// See https://wiki.hydrogenaud.io/index.php?title=Fraunhofer_FDK_AAC#Bitrate_Modes
enum AacVariableBitRate {
V1 = 1;
V2 = 2;
V3 = 3;
V4 = 4;
V5 = 5;
};
union AacBitRate {
1: AacConstantBitRate constant;
2: AacVariableBitRate variable;
};
enum AacAudioObjectType {
/// MPEG-2 Low Complexity
MPEG2_AAC_LC = 0;
};
struct AacEncoderSettings {
AacTransport transport;
AacChannelMode channel_mode;
AacBitRate bit_rate;
AacAudioObjectType aot;
};
/// Customization of h264 encoder parameters for macroblock quantization. The values
/// can range from 0 to 51, with lower numbers indicating higher
/// quality/bitrate. While encoders should support these fields if feasible,
/// some encoders may ignore these fields. It's ok to not set this table, or
/// not set some of the fields in this table, as encoders can determine their
/// own defaults. If the targeted bitrate can't be achieved with the specified values,
/// then the user should expect the resulting encoded stream bitrate to differ from
/// the requested bitrate.
table H264QuantizationParameters {
/// Starting value for quantization of key frames.
1: uint32 i_base;
/// Smallest allowed value for quantization of key frames.
2: uint32 i_min;
/// Largest allowed value for quantization of key frames.
3: uint32 i_max;
/// Starting value for quantization of predicted frames.
4: uint32 p_base;
/// Smallest allowed value for quantization of predicted frames.
5: uint32 p_min;
/// Largest allowed value for quantization of predicted frames.
6: uint32 p_max;
};
/// Settings for H264 Encoders.
table H264EncoderSettings {
/// Target bits per second for encoded stream. Defaults to 200,000 if
/// omitted.
1: uint32 bit_rate;
/// Target frames per second for encoded stream. Defaults to 30 if omitted.
2: uint32 frame_rate;
/// Number of pictures per keyframe. Defaults to 8 if omitted. Setting to 0
/// will disable key frame encoding, except for if force_key_frame is set to
/// true.
3: uint32 gop_size;
/// Whether to enable frame rate adjustments in order to meet target bitrate.
/// False if omitted.
4: bool variable_frame_rate;
/// Lowest frame rate allowed if `variable_frame_rate` is enabled. Defaults
/// to 10 if omitted.
5: uint32 min_frame_rate;
/// If true, next frame encoded will be a key frame. If omitted, defaults to
/// false.
6: bool force_key_frame;
/// Allow customization of quantization parameters for encoding. Each frame
/// submitted after setting this will use the new values. If omitted, no
/// change from encoder defaults is made.
7: H264QuantizationParameters quantization_params;
};
/// Settings for HEVC/H265 Encoders.
table HevcEncoderSettings {
/// Target bits per second for encoded stream. Defaults to 200,000 if
/// omitted.
1: uint32 bit_rate;
/// Target frames per second for encoded stream. Defaults to 30 if omitted.
2: uint32 frame_rate;
/// Number of pictures per keyframe. Defaults to 8 if omitted.
3: uint32 gop_size;
};
/// Settings for encoders that tell them how to encode raw
/// formats.
flexible union EncoderSettings {
1: SbcEncoderSettings sbc;
2: AacEncoderSettings aac;
3: H264EncoderSettings h264;
4: HevcEncoderSettings hevc;
};
/// FormatDetails
///
/// This describes/details the format on input or output of a StreamProcessor
/// (separate instances for input vs. output).
//
// The purpose of FormatDetails is to fill in additional details not
// conveyed via other means.
//
// For decoder input, the format details tend to be fairly sparse, since most
// compressed formats tend to be mostly self-describing.
//
// For decoder output and encoder input, the format details need to include all
// the out-of-band information regarding the uncompressed data, which tends not
// to be self-describing.
//
// Settings that are completely redundant with the data in the format itself
// should not be in a required field here. An encoder may set oob_bytes on its
// output.
//
// This stuff should be limited to things we need to know to properly process the
// data which we can't already determine from the data itself, and which isn't
// already covered by a format's defined OOB binary config blob, which is
// conveyed in oob_bytes.
//
// Most decoders can have FormatDetails.domain null.
table FormatDetails {
// Particular instances of FormatDetails will set this field to make it
// easier for a receiver to determine if any part of the format has changed
// vs. the last FormatDetails received for the same context.
1: uint64 format_details_version_ordinal;
// "mime_type" strings used by particular decoders / encoders so far:
//
// SW AAC decoder:
// * input:
// * "audio/aac-adts" - ATDS AAC; self-contained format, but
// implementation for now requires oob_bytes to contain
// AudioSpecificConfig() reconstructed from ADTS header data - see
// also make_AudioSpecificConfig_from_ADTS_header() for now.
// * output:
// * "audio/raw" - stereo linear 16 bit integer PCM
//
// TODO(dustingreen): avoid requiring oob_bytes when using SoftAAC2.cpp
// for AAC ADTS.
//
// TODO(dustingreen): Add non-ADTS AAC support (which naturally needs
// oob_bytes).
//
// TODO(dustingreen): Consider "pseudo_mime_type", or an enum, + "domain"
// details as needed instead, since calling this "mime_type" could lead to
// confusion.
2: string mime_type;
// Some streams have their own binary configuration structure. For those
// streams we allow that binary structure to be directly conveyed to the
// stream processor here.
//
// audio/aac - this is an AudioSpecificConfig().
// audio/aac-adts - this is not set.
// TODO(dustingreen): make the audio/aac-adts statement true soon. At the
// moment we set this with make_AudioSpecificConfig_from_ADTS_header(), but
// that should not be the client's job for ADTS.
//
// For some formats whose "ES" data format is self-contained, or for which
// there is no format-defined binary OOB config, this is null.
//
// A server can close the channel if the count of bytes is >
// kMaxOobBytesSize or is larger than makes any sense for the stream
// processor. If any stream actually needs more than kMaxOobBytesSize
// bytes here, we could potentially increase this restriction some, but
// this interface isn't designed to support OOB config blobs that approach
// ZX_CHANNEL_MAX_MSG_BYTES.
3: bytes oob_bytes;
// Decoder input format:
//
// If a format is not self-describing given the mime_type and a
// format-spec-defined oob_bytes, this domain field can be set to
// provide the additional compressed-format-specific details. This is
// expected to be fairly rare, so most compressed input formats will have
// only the mime_type and possibly oob_bytes set, with domain typically
// null. If an encoder is upstream however, domain may be set to convey the
// encoder settings that were used, but a decoder consumer doesn't need to
// look at those.
//
// Encoder output format:
//
// The encoder's compressed data output typically needs some configuration
// (provided in this field) that's convenient to provide in a form that's
// not oob_bytes, and the codec can convert that config to oob_bytes on
// encoder output via OnOutputConstraints(). We retain these encoder settings
// in the output FormatDetails to allow for cases where a downstream
// consumer knowing the encoder settings could be useful.
//
// TODO(dustingreen): Decide if we want to retain this, or if we'd prefer to
// split out config settings and maybe only represent a few encoder settings
// as best-effort optional aux data, like bitrate.
//
// Encoder input format / decoder output format:
//
// This field contains fairly detailed information re. uncompressed data
// format details, which tends to _not_ be self-describing in-band.
4: DomainFormat domain;
// See comments above on Parameter. At the time we lock relevant FIDL
// interfaces, there should be zero use of this field outside tests, but
// this is here in case we need to allow a stream processor client to
// convey additional config parameters to/from a stream processor which we
// didn't anticipate before locking.
//
// If there are any known "official" exceptions to the previous paragraph,
// we'll list them here by corresponding mime_type (none so far):
// * "<mime_type>" - <usage_description>
//
// For streams that define their own stream-specific config/OOB data, put
// that in oob_bytes above instead of this field.
5: vector<Parameter> pass_through_parameters;
/// Instructs an encoder on how to encode raw data.
///
/// Decoders may ignore this field but are entitled to rejected requests with
/// this field set because it doesn't make sense.
6: EncoderSettings encoder_settings;
/// The number of ticks of the timebase of input packet timestamp_ish values
/// per second.
///
/// The timebase is only used used for optional extrapolation of timestamp_ish
/// values when an input timestamp which applies to byte 0 of the valid portion
/// of the input packet does not correspond directly to byte 0 of the valid
/// portion of any output packet.
///
/// Leave unset if timestamp extrapolation is not needed, either due to lack of
/// timestamps on input, or due to input being provided in increments of the
/// encoder's input chunk size (based on the encoder settings and calculated
/// independently by the client). Set if timestamp extrapolation is known to be
/// needed or known to be acceptable to the client.
7: uint64 timebase;
};