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h264 example (#19): convert to Annex B

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This works. Unsure why the default AVC doesn't.
This commit is contained in:
Scott Lamb 2022-07-19 15:07:19 -07:00
parent c4b83f1eb9
commit 506613edca
1 changed files with 48 additions and 8 deletions
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56
examples/ffmpeg-decode/src/main.rs
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@ -14,6 +14,9 @@ use std::{fs::File, io::Write, str::FromStr, sync::Arc};
use structopt::StructOpt;
/// Decodes H.264 streams using ffmpeg, writing them into `frame<i>.ppm` images.
///
/// TODO: this only appears to generate proper images with
/// `--convert-to-annex-b`. Unsure why the default AVC isn't working.
#[derive(StructOpt)]
struct Opts {
/// `rtsp://` URL to connect to.
@ -35,6 +38,9 @@ struct Opts {
/// The transport to use: `tcp` or `udp` (experimental).
#[structopt(default_value, long)]
transport: retina::client::Transport,
#[structopt(long)]
convert_to_annex_b: bool,
}
fn init_logging() -> mylog::Handle {
@ -67,12 +73,15 @@ struct H264Processor {
decoder: ffmpeg::codec::decoder::Video,
scaler: Option<ffmpeg::software::scaling::Context>,
frame_i: u64,
convert_to_annex_b: bool,
}
impl H264Processor {
fn new() -> Self {
fn new(convert_to_annex_b: bool) -> Self {
let mut codec_opts = ffmpeg::Dictionary::new();
codec_opts.set("is_avc", "1");
if !convert_to_annex_b {
codec_opts.set("is_avc", "1");
}
let codec = ffmpeg::codec::decoder::find(ffmpeg::codec::Id::H264).unwrap();
let decoder = ffmpeg::codec::decoder::Decoder(ffmpeg::codec::Context::new())
.open_as_with(codec, codec_opts)
@ -83,12 +92,18 @@ impl H264Processor {
decoder,
scaler: None,
frame_i: 0,
convert_to_annex_b,
}
}
fn handle_parameters(&mut self, p: &VideoParameters) -> Result<(), Error> {
let pkt = ffmpeg::codec::packet::Packet::borrow(p.extra_data());
self.decoder.send_packet(&pkt)?;
if !self.convert_to_annex_b {
let pkt = ffmpeg::codec::packet::Packet::borrow(p.extra_data());
self.decoder.send_packet(&pkt)?;
} else {
// TODO: should convert and supply SPS/PPS, rather than relying on
// them existing in-band within frames.
}
// ffmpeg doesn't appear to actually handle the parameters until the
// first full frame, so just note that the scaler needs to be
@ -97,8 +112,12 @@ impl H264Processor {
Ok(())
}
fn send_frame(&mut self, f: &VideoFrame) -> Result<(), Error> {
let pkt = ffmpeg::codec::packet::Packet::borrow(f.data());
fn send_frame(&mut self, f: VideoFrame) -> Result<(), Error> {
let mut data = f.into_data();
if self.convert_to_annex_b {
convert_h264(&mut data)?;
}
let pkt = ffmpeg::codec::packet::Packet::borrow(&data);
self.decoder.send_packet(&pkt)?;
self.receive_frames()?;
Ok(())
@ -158,6 +177,27 @@ impl H264Processor {
}
}
/// Converts from AVC representation to the Annex B representation.
fn convert_h264(data: &mut [u8]) -> Result<(), Error> {
let mut i = 0;
while i < data.len() - 3 {
// Replace each NAL's length with the Annex B start code b"\x00\x00\x00\x01".
let len = u32::from_be_bytes([data[i], data[i + 1], data[i + 2], data[i + 3]]) as usize;
data[i] = 0;
data[i + 1] = 0;
data[i + 2] = 0;
data[i + 3] = 1;
i += 4 + len;
if i > data.len() {
bail!("partial NAL body");
}
}
if i < data.len() {
bail!("partial NAL length");
}
Ok(())
}
async fn run() -> Result<(), Error> {
let opts = Opts::from_args();
ffmpeg::init().unwrap();
@ -200,7 +240,7 @@ async fn run() -> Result<(), Error> {
false
})
.ok_or_else(|| anyhow!("No h264 video stream found"))?;
let mut processor = H264Processor::new();
let mut processor = H264Processor::new(opts.convert_to_annex_b);
session
.setup(
video_stream_i,
@ -229,7 +269,7 @@ async fn run() -> Result<(), Error> {
};
processor.handle_parameters(v)?;
}
processor.send_frame(&f)?;
processor.send_frame(f)?;
},
Some(Ok(_)) => {},
Some(Err(e)) => {