diff --git a/html/index.html b/html/index.html
index 415f6e5..0725215 100644
--- a/html/index.html
+++ b/html/index.html
@@ -16,6 +16,9 @@
- Get a high-resolution snapshot image from the server.
- Uses resolution specified by -camera-snapshot.height=.
+
+ - /snapshot?max_delay=0 to get a snapshot captured exactly now.
+ - /snapshot?max_delay=300 (default) to get a cached snapshot captured up-to 300 ms in the past.
diff --git a/output/http_jpeg.c b/output/http_jpeg.c
index 897c749..9b2f593 100644
--- a/output/http_jpeg.c
+++ b/output/http_jpeg.c
@@ -3,9 +3,13 @@
#include "output.h"
#include "util/http/http.h"
+#include "util/opts/log.h"
#include "device/buffer.h"
#include "device/buffer_lock.h"
+#define SNAPSHOT_TIMEOUT_MS 3000
+#define SNAPSHOT_DEFAULT_DELAY_PARAM "300"
+
#define PART_BOUNDARY "123456789000000000000987654321"
#define CONTENT_TYPE "image/jpeg"
#define CONTENT_LENGTH "Content-Length"
@@ -20,19 +24,42 @@ static const char *const STREAM_PART = "Content-Type: " CONTENT_TYPE "\r\n" CONT
static const char *const STREAM_BOUNDARY = "\r\n"
"--" PART_BOUNDARY "\r\n";
-int http_snapshot_buf_part(buffer_lock_t *buf_lock, buffer_t *buf, int frame, FILE *stream)
+typedef struct
{
- fprintf(stream, "HTTP/1.1 200 OK\r\n");
- fprintf(stream, "Content-Type: image/jpeg\r\n");
- fprintf(stream, "Content-Length: %zu\r\n", buf->used);
- fprintf(stream, "\r\n");
- fwrite(buf->start, buf->used, 1, stream);
+ FILE *stream;
+ uint64_t start_time_us;
+} http_snapshot_t;
+
+int http_snapshot_buf_part(buffer_lock_t *buf_lock, buffer_t *buf, int frame, http_snapshot_t *snapshot)
+{
+ // Ignore frames that are captured
+ if (buf->captured_time_us < snapshot->start_time_us) {
+ return 0;
+ }
+
+ fprintf(snapshot->stream, "HTTP/1.1 200 OK\r\n");
+ fprintf(snapshot->stream, "Content-Type: image/jpeg\r\n");
+ fprintf(snapshot->stream, "Content-Length: %zu\r\n", buf->used);
+ fprintf(snapshot->stream, "\r\n");
+ fwrite(buf->start, buf->used, 1, snapshot->stream);
return 1;
}
void http_snapshot(http_worker_t *worker, FILE *stream)
{
- int n = buffer_lock_write_loop(&snapshot_lock, 1, 0, (buffer_write_fn)http_snapshot_buf_part, stream);
+ // passing the max_delay=0 will ensure that frame is capture at this exact moment
+ const char *max_delay = http_get_param(worker, "max_delay");
+ if (!max_delay) {
+ max_delay = SNAPSHOT_DEFAULT_DELAY_PARAM;
+ }
+
+ http_snapshot_t snapshot = {
+ .stream = stream,
+ .start_time_us = get_monotonic_time_us(NULL, NULL) - atoi(max_delay) * 1000
+ };
+
+ int n = buffer_lock_write_loop(&snapshot_lock, 1, SNAPSHOT_TIMEOUT_MS,
+ (buffer_write_fn)http_snapshot_buf_part, &snapshot);
if (n <= 0) {
http_500(stream, NULL);
diff --git a/output/output.c b/output/output.c
index c19aa25..192f976 100644
--- a/output/output.c
+++ b/output/output.c
@@ -1,5 +1,5 @@
#include "device/buffer_lock.h"
-DEFINE_BUFFER_LOCK(snapshot_lock, 1000);
+DEFINE_BUFFER_LOCK(snapshot_lock, 0);
DEFINE_BUFFER_LOCK(stream_lock, 0);
DEFINE_BUFFER_LOCK(video_lock, 0);
diff --git a/util/http/http.c b/util/http/http.c
index 1c5ea28..0957ff7 100644
--- a/util/http/http.c
+++ b/util/http/http.c
@@ -84,6 +84,19 @@ void *http_enum_params(http_worker_t *worker, FILE *stream, http_param_fn fn, vo
return ret;
}
+static void *http_get_param_fn(struct http_worker_s *worker, FILE *stream, const char *key, const char *value, void *opaque)
+{
+ if (!strcmp(key, opaque))
+ return (void*)value;
+
+ return NULL;
+}
+
+const char *http_get_param(http_worker_t *worker, const char *key)
+{
+ return http_enum_params(worker, NULL, http_get_param_fn, (void*)key);
+}
+
static void http_process(http_worker_t *worker, FILE *stream)
{
// Read headers
diff --git a/util/http/http.h b/util/http/http.h
index 1dc4d6a..f9b0e6c 100644
--- a/util/http/http.h
+++ b/util/http/http.h
@@ -62,3 +62,4 @@ void http_400(FILE *stream, const char *data);
void http_404(FILE *stream, const char *data);
void http_500(FILE *stream, const char *data);
void *http_enum_params(http_worker_t *worker, FILE *stream, http_param_fn fn, void *opaque);
+const char *http_get_param(http_worker_t *worker, const char *key);