Struct Mp4StreamingDemuxer 

pub struct Mp4StreamingDemuxer { /* private fields */ }

MP4 / MOV streaming demuxer. Owns the input bytes (so its Mp4Reader<Cursor<Vec<u8>>> cursor is self-contained) and walks read_sample(track_id, idx) one sample at a time. Per-sample AVCC→Annex-B + parameter-set tracking (Squad-14) is preserved. Per-sample location record built when the input is a fragmented MP4. The mp4 crate (v0.14) returns garbage (typically the bytes of an adjacent moof box) from read_sample on fragmented inputs — affects BOTH video and audio tracks. Side-stepping read_sample for fragmented input by pre-computing sample (file_offset, size, pts, duration) from the moof->traf->trun chain produces correct bytes regardless of track kind. The track filter is track_id (parameter on the walker chain) — generic across video/audio/anything else with a track_id.

Bug history: the audio-extraction path WAS originally claimed to “walk boxes itself” (per a prior comment here) but in fact it called reader.read_sample(audio_track_id, idx) — the same buggy path video uses. Burned 2026-05-09: malformed audio segments (8-byte first AU containing the source’s moof header bytes 00 00 NN NN 6d 6f 6f 66, every following AU mid-box-tree) passed dedup hash unchanged because they’re size-deterministic per source, MSE rejected them with Number of bands exceeds limit → SourceBuffer error → MediaSource readyState ended → all video appendBuffer calls failed.

Trait Implementations

impl StreamingDemuxer for Mp4StreamingDemuxer

fn header(&self) -> &DemuxHeader

Header info parsed from the container header. Cheap to call — returns a borrow of the cached DemuxHeader populated at construction time.

fn next_video_sample(&mut self) -> Result<Option<Sample>>

Pull the next video sample. Returns Ok(None) at EOF. Allocates a fresh Vec per sample; nothing is retained internally beyond the reader’s per-format cursor state.

fn audio(&self) -> Option<&AudioTrack>

Audio is a single buffered slab populated at construction time (Squad-18/23/27 passthrough pattern). Streaming audio is out of scope for this sprint per the pinned design.