99#include < sys/ioctl.h>
1010#include < linux/videodev2.h>
1111
12+ #include < string>
1213#include < vector>
1314#include < set>
1415#include < stdexcept>
2122// Obviously, this won't help if multiple processes are used
2223// or if devices are opened by other tools.
2324// In this case, explicitly specifying the device seems the only solution.
24- static std::set<size_t > ACTIVE_DEVICES;
25+ static std::set<std::string > ACTIVE_DEVICES;
2526
2627class VirtualOutput {
2728 private:
2829 bool _output_running = false ;
2930 int _camera_fd;
3031 std::string _camera_device;
31- size_t _camera_device_idx;
3232 uint32_t _frame_fourcc;
3333 uint32_t _native_fourcc;
3434 uint32_t _frame_width;
@@ -37,7 +37,8 @@ class VirtualOutput {
3737 std::vector<uint8_t > _buffer_output;
3838
3939 public:
40- VirtualOutput (uint32_t width, uint32_t height, uint32_t fourcc) {
40+ VirtualOutput (uint32_t width, uint32_t height, uint32_t fourcc,
41+ std::optional<std::string> device_) {
4142 _frame_width = width;
4243 _frame_height = height;
4344 _frame_fourcc = libyuv::CanonicalFourCC (fourcc);
@@ -82,50 +83,78 @@ class VirtualOutput {
8283 throw std::runtime_error (" Unsupported image format."
8384 }
8485
85- char device_name[14 ];
86- int device_idx = -1 ;
87-
88- for (size_t i = 0 ; i < 100 ; i++) {
89- if (ACTIVE_DEVICES.count (i)) {
90- continue ;
86+ auto try_open = [&](const std::string& device_name) {
87+ if (ACTIVE_DEVICES.count (device_name)) {
88+ throw std::invalid_argument (
89+ " Device " " is already in use."
90+ );
9191 }
92- sprintf (device_name, " /dev/video%zu"
93- _camera_fd = open (device_name, O_WRONLY | O_SYNC);
92+ _camera_fd = open (device_name.c_str (), O_WRONLY | O_SYNC);
9493 if (_camera_fd == -1 ) {
9594 if (errno == EACCES) {
9695 throw std::runtime_error (
97- " Could not access " std::string ( device_name) + " due to missing permissions. "
96+ " Could not access " " due to missing permissions. "
9897 " Did you add your user to the 'video' group? "
9998 " Run 'usermod -a -G video myusername' and log out and in again."
10099 );
100+ } else if (errno == ENOENT) {
101+ throw std::invalid_argument (
102+ " Device " " does not exist."
103+ );
104+ } else {
105+ throw std::invalid_argument (
106+ " Device " " could not be opened: "
107+ std::string (strerror (errno))
108+ );
101109 }
102- continue ;
103110 }
104111
105112 struct v4l2_capability camera_cap;
106113
107114 if (ioctl (_camera_fd, VIDIOC_QUERYCAP, &camera_cap) == -1 ) {
108- continue ;
115+ throw std::invalid_argument (
116+ " Device capabilities of " " could not be queried."
117+ );
109118 }
110119 if (!(camera_cap.capabilities & V4L2_CAP_VIDEO_OUTPUT)) {
111- continue ;
120+ throw std::invalid_argument (
121+ " Device " " is not a video output device."
122+ );
112123 }
113124 if (strcmp ((const char *)camera_cap.driver , " v4l2 loopback" 0 ) {
114- continue ;
125+ throw std::invalid_argument (
126+ " Device " " is not a V4L2 device."
127+ );
128+ }
129+ };
130+
131+ std::string device_name;
132+
133+ if (device_.has_value ()) {
134+ device_name = device_.value ();
135+ try_open (device_name);
136+ } else {
137+ bool found = false ;
138+ for (size_t i = 0 ; i < 100 ; i++) {
139+ std::ostringstream device_name_s;
140+ device_name_s << " /dev/video"
141+ device_name = device_name_s.str ();
142+ try {
143+ try_open (device_name);
144+ } catch (std::invalid_argument&) {
145+ continue ;
146+ }
147+ found = true ;
148+ break ;
149+ }
150+ if (!found) {
151+ throw std::runtime_error (
152+ " No v4l2 loopback device found at /dev/video[0-99]. "
153+ " Did you run 'modprobe v4l2loopback'? "
154+ " See also pyvirtualcam's documentation."
115155 }
116- device_idx = i;
117- break ;
118- }
119- if (device_idx == -1 ) {
120- throw std::runtime_error (
121- " No v4l2 loopback device found at /dev/video[0-99]. "
122- " Did you run 'modprobe v4l2loopback'? "
123- " See also pyvirtualcam's documentation."
124156 }
125157
126- uint32_t half_width = width / 2 ;
127- uint32_t half_height = height / 2 ;
128-
129158 v4l2_format v4l2_fmt;
130159 memset (&v4l2_fmt, 0 , sizeof (v4l2_fmt));
131160 v4l2_fmt.type = V4L2_BUF_TYPE_VIDEO_OUTPUT;
@@ -139,16 +168,15 @@ class VirtualOutput {
139168 if (ioctl (_camera_fd, VIDIOC_S_FMT, &v4l2_fmt) == -1 ) {
140169 close (_camera_fd);
141170 throw std::runtime_error (
142- " Virtual camera device " std::string ( device_name) +
171+ " Virtual camera device "
143172 " could not be configured: " std::string (strerror (errno))
144173 );
145174 }
146175
147176 _output_running = true ;
148- _camera_device = std::string (device_name);
149- _camera_device_idx = device_idx;
177+ _camera_device = device_name;
150178
151- ACTIVE_DEVICES.insert (device_idx );
179+ ACTIVE_DEVICES.insert (_camera_device );
152180 }
153181
154182 void stop () {
@@ -159,7 +187,7 @@ class VirtualOutput {
159187 close (_camera_fd);
160188
161189 _output_running = false ;
162- ACTIVE_DEVICES.erase (_camera_device_idx );
190+ ACTIVE_DEVICES.erase (_camera_device );
163191 }
164192
165193 void send (const uint8_t * frame) {
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