| // Copyright 2019 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. |
| |
| use crate::{elementary_stream::*, Result}; |
| use fidl_fuchsia_media::FormatDetails; |
| use std::{fs, path::Path}; |
| |
| pub const BEAR_TEST_FILE: &str = "/pkg/data/bear.h264"; |
| |
| /// Represents an H264 elementary stream. |
| pub struct H264Stream { |
| data: Vec<u8>, |
| } |
| |
| impl H264Stream { |
| /// Constructs an H264 elementary stream from a file with raw elementary stream data. |
| pub fn from_file(filename: impl AsRef<Path>) -> Result<Self> { |
| Ok(Self { data: fs::read(filename)? }) |
| } |
| |
| /// Returns an iterator over H264 NALs that does not copy. |
| fn nal_iter(&self) -> impl Iterator<Item = H264Nal> { |
| H264NalIter { data: &self.data, pos: 0 } |
| } |
| } |
| |
| impl ElementaryStream for H264Stream { |
| fn format_details(&self, version_ordinal: u64) -> FormatDetails { |
| FormatDetails { |
| format_details_version_ordinal: Some(version_ordinal), |
| mime_type: Some(String::from("video/h264")), |
| oob_bytes: None, |
| domain: None, |
| pass_through_parameters: None, |
| } |
| } |
| |
| fn is_access_units(&self) -> bool { |
| true |
| } |
| |
| fn stream<'a>(&'a self) -> Box<dyn Iterator<Item = ElementaryStreamChunk> + 'a> { |
| Box::new(self.nal_iter().map(|nal| ElementaryStreamChunk { |
| start_access_unit: true, |
| known_end_access_unit: true, |
| data: nal.data, |
| significance: match nal.kind { |
| H264NalKind::Picture => Significance::Video(VideoSignificance::Picture), |
| H264NalKind::NotPicture => Significance::Video(VideoSignificance::NotPicture), |
| }, |
| timestamp: None, |
| })) |
| } |
| } |
| |
| pub struct H264Nal<'a> { |
| pub kind: H264NalKind, |
| pub data: &'a [u8], |
| } |
| |
| pub enum H264NalKind { |
| Picture, |
| NotPicture, |
| } |
| |
| impl H264NalKind { |
| const NON_IDR_PICTURE_CODE: u8 = 1; |
| const IDR_PICTURE_CODE: u8 = 5; |
| |
| fn from_header(header: u8) -> Self { |
| let kind = header & 0xf; |
| if kind == Self::NON_IDR_PICTURE_CODE || kind == Self::IDR_PICTURE_CODE { |
| H264NalKind::Picture |
| } else { |
| H264NalKind::NotPicture |
| } |
| } |
| } |
| |
| struct H264NalStart<'a> { |
| /// Position in the h264 stream of the start. |
| pos: usize, |
| /// All the data from the start of the NAL onward. |
| data: &'a [u8], |
| kind: H264NalKind, |
| } |
| |
| /// An iterator over NALs in an H264 stream. |
| struct H264NalIter<'a> { |
| data: &'a [u8], |
| pos: usize, |
| } |
| |
| impl<'a> H264NalIter<'a> { |
| fn next_nal(&self, pos: usize) -> Option<H264Nal<'a>> { |
| // This won't need to search if pos already at a start code. |
| let nal_start = self.next_nal_start(pos)?; |
| // We search 3 bytes after the found nal's start, because that will |
| // ensure we don't just find the same start code again. |
| match self.next_nal_start(nal_start.pos + 3) { |
| Some(next_start) => Some(H264Nal { |
| kind: nal_start.kind, |
| data: &nal_start.data[0..(next_start.pos - nal_start.pos)], |
| }), |
| None => Some(H264Nal { kind: nal_start.kind, data: nal_start.data }), |
| } |
| } |
| |
| fn next_nal_start(&self, pos: usize) -> Option<H264NalStart<'a>> { |
| // This search size will find 3 and 4 byte start codes, and the |
| // header value. |
| const NAL_SEARCH_SIZE: usize = 5; |
| |
| let data = self.data.get(pos..)?; |
| data.windows(NAL_SEARCH_SIZE).enumerate().find_map(|(i, candidate)| match candidate { |
| [0, 0, 0, 1, h] | [0, 0, 1, h, _] => Some(H264NalStart { |
| pos: i + pos, |
| data: data.get(i..).expect("Getting slice starting where we just matched"), |
| kind: H264NalKind::from_header(*h), |
| }), |
| _ => None, |
| }) |
| } |
| } |
| |
| impl<'a> Iterator for H264NalIter<'a> { |
| type Item = H264Nal<'a>; |
| fn next(&mut self) -> Option<Self::Item> { |
| let nal = self.next_nal(self.pos); |
| self.pos += nal.as_ref().map(|n| n.data.len()).unwrap_or(0); |
| nal |
| } |
| } |