-
Notifications
You must be signed in to change notification settings - Fork 62
/
stream_forward_mmap.rs
101 lines (84 loc) · 3.92 KB
/
stream_forward_mmap.rs
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
use std::io;
use std::time::Instant;
use v4l::buffer::Type;
use v4l::io::traits::{CaptureStream, OutputStream};
use v4l::prelude::*;
use v4l::video::{Capture, Output};
fn main() -> io::Result<()> {
let source = "/dev/video0";
println!("Using source device: {}\n", source);
// Determine which device to use
let sink = "/dev/video1";
println!("Using sink device: {}\n", sink);
// Capture 4 frames by default
let count = 4;
// Allocate 4 buffers by default
let buffer_count = 4;
let cap = Device::with_path(source)?;
println!("Active cap capabilities:\n{}", cap.query_caps()?);
println!("Active cap format:\n{}", Capture::format(&cap)?);
println!("Active cap parameters:\n{}", Capture::params(&cap)?);
let out = Device::with_path(sink)?;
println!("Active out capabilities:\n{}", out.query_caps()?);
println!("Active out format:\n{}", Output::format(&out)?);
println!("Active out parameters:\n{}", Output::params(&out)?);
// BEWARE OF DRAGONS
// Buggy drivers (such as v4l2loopback) only set the v4l2 buffer size (length field) once
// a format is set, even though a valid format appears to be available when doing VIDIOC_G_FMT!
// In our case, we just (try to) enforce the source format on the sink device.
let source_fmt = Capture::format(&cap)?;
let sink_fmt = Output::set_format(&out, &source_fmt)?;
if source_fmt.width != sink_fmt.width
|| source_fmt.height != sink_fmt.height
|| source_fmt.fourcc != sink_fmt.fourcc
{
return Err(io::Error::new(
io::ErrorKind::Other,
"failed to enforce source format on sink device",
));
}
println!("New out format:\n{}", Output::format(&out)?);
// Setup a buffer stream and grab a frame, then print its data
let mut cap_stream = MmapStream::with_buffers(&cap, Type::VideoCapture, buffer_count)?;
let mut out_stream = MmapStream::with_buffers(&out, Type::VideoOutput, buffer_count)?;
// warmup
CaptureStream::next(&mut cap_stream)?;
let start = Instant::now();
let mut megabytes_ps: f64 = 0.0;
for i in 0..count {
let t0 = Instant::now();
let (buf_in, buf_in_meta) = CaptureStream::next(&mut cap_stream)?;
let (buf_out, buf_out_meta) = OutputStream::next(&mut out_stream)?;
// Output devices generally cannot know the exact size of the output buffers for
// compressed formats (e.g. MJPG). They will however allocate a size that is always
// large enough to hold images of the format in question. We know how big a buffer we need
// since we control the input buffer - so just enforce that size on the output buffer.
let buf_out = &mut buf_out[0..buf_in.len()];
buf_out.copy_from_slice(buf_in);
buf_out_meta.field = 0;
buf_out_meta.bytesused = buf_in_meta.bytesused;
let duration_us = t0.elapsed().as_micros();
let cur = buf_in.len() as f64 / 1_048_576.0 * 1_000_000.0 / duration_us as f64;
if i == 0 {
megabytes_ps = cur;
} else {
// ignore the first measurement
let prev = megabytes_ps * (i as f64 / (i + 1) as f64);
let now = cur * (1.0 / (i + 1) as f64);
megabytes_ps = prev + now;
}
println!("Buffer");
println!(" sequence [in] : {}", buf_in_meta.sequence);
println!(" sequence [out] : {}", buf_out_meta.sequence);
println!(" timestamp [in] : {}", buf_in_meta.timestamp);
println!(" timestamp [out] : {}", buf_out_meta.timestamp);
println!(" flags [in] : {}", buf_in_meta.flags);
println!(" flags [out] : {}", buf_out_meta.flags);
println!(" length [in] : {}", buf_in.len());
println!(" length [out] : {}", buf_out.len());
}
println!();
println!("FPS: {}", count as f64 / start.elapsed().as_secs_f64());
println!("MB/s: {}", megabytes_ps);
Ok(())
}