Struct AudioInfo 

pub struct AudioInfo {
    pub codec: String,
    pub sample_rate: u32,
    pub channels: u16,
    pub timescale: u32,
    pub asc_bytes: Vec<u8>,
    pub codec_private: Vec<u8>,
}

Parameters required to bolt an audio track onto Av1Mp4Muxer.

Four codec families are supported:

• AAC-LC (Squad-18, task #63 v1): mono or stereo, sample_rate as the mdhd timescale per ISO/IEC 14496-14 standard practice, and the AudioSpecificConfig surfaced verbatim from the demuxer (see demux::AudioTrack::asc) so HE-AAC / xHE-AAC signalling bits survive the passthrough intact. Sample entry: mp4a + esds.
• Opus (Squad-23): mono or stereo, sample_rate is the source’s InputSampleRate (typically 48000), mdhd timescale is pinned at 48000 per RFC 7845 §3 (Opus internally always operates at 48 kHz). Sample entry: Opus (4cc per RFC 7845 §4.4 — capital O) + dOps (Opus-Specific Box per §4.5). The OpusHead body bytes are carried in codec_private and emitted verbatim inside dOps.
• AC-3 / Dolby Digital (Squad-26): up to 5.1 channels, sample_rate from the source’s syncframe (32 / 44.1 / 48 kHz). Sample entry: ac-3 + dac3 (ETSI TS 102 366 §F.4 / Annex F). The 3-byte dac3 body is carried in codec_private and emitted verbatim.
• E-AC-3 / Dolby Digital Plus (Squad-26): up to 5.1 channels in v1 scope (single independent substream). Sample entry: ec-3 + dec3 (ETSI TS 102 366 §F.6). The dec3 body is carried in codec_private and emitted verbatim.

Discriminator: codec field. "aac" → AAC path; "opus" → Opus path; "ac3" → AC-3 path; "eac3" → E-AC-3 path. Anything else is rejected at with_audio() time.

Fields

codec: String

Human-readable codec tag. Muxer accepts "aac" (case-insensitive) and "opus" (case-insensitive). Anything else is rejected with a clear error — this is intentional (no stubs).

sample_rate: u32

Audio sample rate in Hz. For AAC: typically 44100 / 48000; doubles as the mdhd timescale. For Opus: the source’s InputSampleRate (informational; the mdhd timescale is pinned to 48000 per RFC 7845 regardless of this value).

channels: u16

Channel count. Both codecs support 1 (mono) and 2 (stereo) only; the muxer bails on other values.

timescale: u32

Audio timescale in ticks per second. AAC: equals sample_rate. Opus: caller should pass 48000 (RFC 7845); the muxer additionally validates this for the Opus path.

asc_bytes: Vec<u8>

AudioSpecificConfig bytes verbatim from the demuxer (AAC only). Embedded into the esds box’s DecoderSpecificInfo (tag 0x05) payload. Empty for non-AAC codecs.

codec_private: Vec<u8>

Codec-private body bytes (Opus / AC-3 / E-AC-3). For Opus this MUST be the RFC 7845 §5.1 OpusHead payload (the same bytes a WebM/MKV CodecPrivate element would carry; see RFC 7845 §5.2 for the MKV mapping). Emitted verbatim as the body of the dOps box inside the Opus sample entry. For AC-3 this carries the 3-byte dac3 body (ETSI TS 102 366 §F.4); for E-AC-3 the variable-size dec3 body (§F.6). Empty for AAC.

Layout (RFC 7845 §5.1, 19 bytes minimum for ChannelMappingFamily=0 with the 8-byte ‘OpusHead’ magic prefix; the magic is NOT carried in dOps — only the post-magic body, which is 11 bytes minimum):

• Version u8 = 1 (in OpusHead; mapped to 0 in dOps per §4.5)
• OutputChannelCount u8
• PreSkip u16 LE (in OpusHead; converted to BE for dOps per §4.5)
• InputSampleRate u32 LE (LE in OpusHead, BE in dOps)
• OutputGain i16 LE (LE in OpusHead, BE in dOps)
• ChannelMappingFamily u8
• (if family != 0: 1 + 1 + N additional bytes)

The byte-order conversion between OpusHead (Ogg LE convention) and dOps (ISOBMFF BE convention) is handled by build_dops in mux.rs. Callers should pass the OpusHead bytes (LE numeric fields) — that’s the form the MKV / WebM demuxer surfaces directly out of CodecPrivate.

Implementations

impl AudioInfo

pub fn aac_lc(sample_rate: u32, channels: u16, asc_bytes: Vec<u8>) -> Self

Convenience constructor for the AAC-LC path. Mirrors Squad-18’s original API surface so existing AAC call sites stay terse.

pub fn opus( input_sample_rate: u32, channels: u16, codec_private: Vec<u8>, ) -> Self

Convenience constructor for the Opus path. Pins timescale to 48000 per RFC 7845 §3 — Opus is internally always 48 kHz so the mdhd timescale, not the source’s nominal InputSampleRate, is what drives sample-duration math on every player.

pub fn ac3(sample_rate: u32, channels: u16, dac3_body: Vec<u8>) -> Self

Convenience constructor for the AC-3 (Dolby Digital) passthrough path (Squad-26). codec_private carries the 3-byte dac3 body payload (ETSI TS 102 366 §F.4) the muxer writes verbatim into the dac3 box. mdhd timescale = sample_rate (48000 / 44100 / 32000) — AC-3 doesn’t have Opus’s “internally fixed at 48 kHz” rule.

pub fn eac3(sample_rate: u32, channels: u16, dec3_body: Vec<u8>) -> Self

Convenience constructor for the E-AC-3 (Dolby Digital Plus) passthrough path (Squad-26). codec_private carries the dec3 body payload (ETSI TS 102 366 §F.6) — variable size based on substream count; minimum ~5 bytes for the single-independent-substream case.

Trait Implementations

impl Clone for AudioInfo

fn clone(&self) -> AudioInfo

Returns a duplicate of the value.

fn clone_from(&mut self, source: &Self)

Performs copy-assignment from source.

impl Debug for AudioInfo

fn fmt(&self, f: &mut Formatter<'_>) -> Result

Formats the value using the given formatter.