|
| 1 | +use std::time::Duration; |
| 2 | + |
| 3 | +use bytes::BytesMut; |
| 4 | +use tracing::debug; |
| 5 | +use vk_video::parser::h264::{AccessUnit, H264Parser, ParsedNalu, nal_types::slice::SliceFamily}; |
| 6 | + |
| 7 | +use crate::prelude::*; |
| 8 | + |
| 9 | +#[derive(Default)] |
| 10 | +pub struct AUSplitter { |
| 11 | + parser: H264Parser, |
| 12 | + prev_ref_frame_num: u16, |
| 13 | + detected_missed_frames: bool, |
| 14 | +} |
| 15 | + |
| 16 | +impl AUSplitter { |
| 17 | + pub fn put_chunk( |
| 18 | + &mut self, |
| 19 | + chunk: EncodedInputChunk, |
| 20 | + ) -> Result<Vec<EncodedInputChunk>, AUSplitterError> { |
| 21 | + if MediaKind::Video(VideoCodec::H264) != chunk.kind { |
| 22 | + return Err(AUSplitterError::UnsupportedMediaKind(chunk.kind)); |
| 23 | + } |
| 24 | + |
| 25 | + let access_units = self |
| 26 | + .parser |
| 27 | + .parse(&chunk.data, Some(chunk.pts.as_micros() as u64))?; |
| 28 | + |
| 29 | + let mut chunks = Vec::new(); |
| 30 | + for au in access_units { |
| 31 | + self.verify_access_unit(&au)?; |
| 32 | + |
| 33 | + let mut data = BytesMut::new(); |
| 34 | + let pts = match au.0.first().and_then(|nalu| nalu.pts) { |
| 35 | + Some(pts) => pts, |
| 36 | + None => { |
| 37 | + debug!("Expected access unit with pts. Skipping the access unit"); |
| 38 | + continue; |
| 39 | + } |
| 40 | + }; |
| 41 | + |
| 42 | + // Parser returns nalus which may not start with a start code |
| 43 | + // but each nalu always ends with the start code of the next nalu, |
| 44 | + // so we have to make sure that there is a start code in the beginning |
| 45 | + const START_CODES: [&[u8]; 2] = [&[0, 0, 0, 1], &[0, 0, 1]]; |
| 46 | + if let Some(first_nalu) = au.0.first() { |
| 47 | + let has_start_code = START_CODES |
| 48 | + .iter() |
| 49 | + .any(|code| first_nalu.raw_bytes.starts_with(code)); |
| 50 | + if !has_start_code { |
| 51 | + data.extend_from_slice(&[0, 0, 1]); |
| 52 | + } |
| 53 | + } |
| 54 | + |
| 55 | + for nalu in au.0.iter() { |
| 56 | + data.extend_from_slice(&nalu.raw_bytes); |
| 57 | + } |
| 58 | + |
| 59 | + chunks.push(EncodedInputChunk { |
| 60 | + data: data.freeze(), |
| 61 | + pts: Duration::from_micros(pts), |
| 62 | + dts: None, |
| 63 | + kind: MediaKind::Video(VideoCodec::H264), |
| 64 | + }); |
| 65 | + } |
| 66 | + |
| 67 | + Ok(chunks) |
| 68 | + } |
| 69 | + |
| 70 | + fn verify_access_unit(&mut self, au: &AccessUnit) -> Result<(), AUSplitterError> { |
| 71 | + let Some(ParsedNalu::Slice(slice)) = |
| 72 | + au.0.iter() |
| 73 | + .map(|nalu| &nalu.parsed) |
| 74 | + .find(|nalu| matches!(nalu, ParsedNalu::Slice(_))) |
| 75 | + else { |
| 76 | + return Err(AUSplitterError::InvalidAccessUnit); |
| 77 | + }; |
| 78 | + |
| 79 | + match slice.header.slice_type.family { |
| 80 | + SliceFamily::P | SliceFamily::B => { |
| 81 | + let sps = &slice.sps; |
| 82 | + let frame_num = slice.header.frame_num; |
| 83 | + let max_frame_num = 1i64 << sps.log2_max_frame_num(); |
| 84 | + |
| 85 | + let is_expected_frame_num = !sps.gaps_in_frame_num_value_allowed_flag |
| 86 | + && frame_num != self.prev_ref_frame_num |
| 87 | + && frame_num != ((self.prev_ref_frame_num as i64 + 1) % max_frame_num) as u16; |
| 88 | + if is_expected_frame_num || self.detected_missed_frames { |
| 89 | + debug!("AUSplitter detected missing frame"); |
| 90 | + self.detected_missed_frames = true; |
| 91 | + return Err(AUSplitterError::MissingReferenceFrame); |
| 92 | + } |
| 93 | + |
| 94 | + self.prev_ref_frame_num = frame_num; |
| 95 | + } |
| 96 | + SliceFamily::I => { |
| 97 | + self.prev_ref_frame_num = 0; |
| 98 | + self.detected_missed_frames = false; |
| 99 | + } |
| 100 | + SliceFamily::SP | SliceFamily::SI => {} // Not supported |
| 101 | + } |
| 102 | + Ok(()) |
| 103 | + } |
| 104 | +} |
| 105 | + |
| 106 | +#[derive(Debug, thiserror::Error)] |
| 107 | +pub enum AUSplitterError { |
| 108 | + #[error("Missing reference frame")] |
| 109 | + MissingReferenceFrame, |
| 110 | + |
| 111 | + #[error("Could not parse H264 chunk: {0}")] |
| 112 | + ParserError(#[from] vk_video::parser::h264::H264ParserError), |
| 113 | + |
| 114 | + #[error("Invalid access unit")] |
| 115 | + InvalidAccessUnit, |
| 116 | + |
| 117 | + #[error("Unsupported media kind {0:?}")] |
| 118 | + UnsupportedMediaKind(MediaKind), |
| 119 | +} |
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