102 lines
2.7 KiB
Go
102 lines
2.7 KiB
Go
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package frame
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import (
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"fmt"
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"sync"
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"time"
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"gocv.io/x/gocv"
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)
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// isCaptureDevice returns true if idx is a real video capture device
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// (not a video output, loopback, tuner, etc.) by checking for a non-zero
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// frame size — only capture devices report this before streaming.
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func isCaptureDevice(idx int) bool {
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if idx < 0 {
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return false
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}
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cam, err := gocv.VideoCaptureDevice(idx)
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if err != nil {
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return false
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}
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defer cam.Close()
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return cam.Get(gocv.VideoCaptureFrameWidth) > 0
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}
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// Scan discovers working V4L camera indices in [min, max].
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// Only real video capture devices are reported — non-capture V4L2 devices
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// (output, loopback, tuners) are filtered out. Each device is opened and
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// immediately closed; handles are never leaked.
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func Scan(min, max int) ([]int, error) {
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return scanRange(min, max, 1, nil)
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}
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// ScanSkip is Scan restricted to every skip-th index in [min, max], so a
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// rebalance pass can re-probe the bus without hammering every device.
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func ScanSkip(min, max, skip int) ([]int, error) {
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return scanRange(min, max, skip, nil)
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}
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// ScanExcluding is Scan that never opens or reports the given indices, so a
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// hotplug loop can re-probe the bus without touching devices it is already
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// streaming from — a busy V4L handle can transiently report a zero size and
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// flap the rebalance into a teardown/restart loop.
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func ScanExcluding(min, max int, exclude map[int]struct{}) ([]int, error) {
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return scanRange(min, max, 1, exclude)
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}
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// ScanSkipExcluding is ScanSkip with an exclusion set, see ScanExcluding.
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func ScanSkipExcluding(min, max, skip int, exclude map[int]struct{}) ([]int, error) {
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return scanRange(min, max, skip, exclude)
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}
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func scanRange(min, max, skip int, exclude map[int]struct{}) ([]int, error) {
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if min > max {
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return nil, fmt.Errorf("empty range [%d, %d]", min, max)
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}
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if skip < 1 {
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skip = 1
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}
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var indices []int
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var mu sync.Mutex
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var wg sync.WaitGroup
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for i := min; i <= max; i += skip {
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if _, excluded := exclude[i]; excluded {
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continue
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}
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wg.Add(1)
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go func(idx int) {
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defer wg.Done()
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if isCaptureDevice(idx) {
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mu.Lock()
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indices = append(indices, idx)
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mu.Unlock()
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}
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}(i)
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}
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wg.Wait()
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if len(indices) == 0 {
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return nil, fmt.Errorf("no cameras found in range [%d, %d]", min, max)
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}
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return indices, nil
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}
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// WaitGroupTimeout waits up to timeout for wg to reach zero, returning false
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// if it times out so shutdown paths can bound how long they stall on workers
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// that are blocked in a downstream retry.
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func WaitGroupTimeout(wg *sync.WaitGroup, timeout time.Duration) bool {
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done := make(chan struct{})
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go func() {
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wg.Wait()
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close(done)
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}()
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select {
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case <-done:
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return true
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case <-time.After(timeout):
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return false
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}
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}
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