lib: add a function to query the decoder frame delay

4 files changed, 30 insertions, 2 deletions

diff --git a/include/dav1d/dav1d.h b/include/dav1d/dav1d.h
index fd3b622..bd70303 100644
--- a/include/dav1d/dav1d.h
+++ b/include/dav1d/dav1d.h
@@ -287,6 +287,21 @@ DAV1D_API int dav1d_get_event_flags(Dav1dContext *c, enum Dav1dEventFlags *flags
  */
 DAV1D_API int dav1d_get_decode_error_data_props(Dav1dContext *c, Dav1dDataProps *out);
 
+/**
+ * Get the decoder delay, which is the number of internally buffered frames, not
+ * including reference frames.
+ * This value is guaranteed to be >= 1 and <= max_frame_delay.
+ *
+ * @param c Input settings context.
+ *
+ * @return Decoder frame delay on success, or < 0 (a negative DAV1D_ERR code) on
+ *         error.
+ *
+ * @note The returned delay is valid only for a Dav1dContext initialized with the
+ *       provided Dav1dSettings.
+ */
+DAV1D_API int dav1d_get_frame_delay(const Dav1dSettings *s);
+
 # ifdef __cplusplus
 }
 # endif
diff --git a/meson.build b/meson.build
index a312ae0..372a55d 100644
--- a/meson.build
+++ b/meson.build
@@ -30,7 +30,7 @@ project('dav1d', ['c'],
                       'b_ndebug=if-release'],
     meson_version: '>= 0.49.0')
 
-dav1d_soname_version       = '6.6.0'
+dav1d_soname_version       = '6.7.0'
 dav1d_api_version_array    = dav1d_soname_version.split('.')
 dav1d_api_version_major    = dav1d_api_version_array[0]
 dav1d_api_version_minor    = dav1d_api_version_array[1]
diff --git a/src/cpu.c b/src/cpu.c
index 2e5e8d9..3d129c8 100644
--- a/src/cpu.c
+++ b/src/cpu.c
@@ -99,6 +99,7 @@ COLD int dav1d_num_logical_processors(Dav1dContext *const c) {
 #elif defined(_SC_NPROCESSORS_ONLN)
     return (int)sysconf(_SC_NPROCESSORS_ONLN);
 #endif
-    dav1d_log(c, "Unable to detect thread count, defaulting to single-threaded mode\n");
+    if (c)
+        dav1d_log(c, "Unable to detect thread count, defaulting to single-threaded mode\n");
     return 1;
 }
diff --git a/src/lib.c b/src/lib.c
index 210b4f3..528198e 100644
--- a/src/lib.c
+++ b/src/lib.c
@@ -116,6 +116,18 @@ static COLD void get_num_threads(Dav1dContext *const c, const Dav1dSettings *con
             *n_tc < 50 ? fc_lut[*n_tc - 1] : 8; // min(8, ceil(sqrt(n)))
 }
 
+COLD int dav1d_get_frame_delay(const Dav1dSettings *const s) {
+    unsigned n_tc, n_fc;
+    validate_input_or_ret(s != NULL, DAV1D_ERR(EINVAL));
+    validate_input_or_ret(s->n_threads >= 0 &&
+                          s->n_threads <= DAV1D_MAX_THREADS, DAV1D_ERR(EINVAL));
+    validate_input_or_ret(s->max_frame_delay >= 0 &&
+                          s->max_frame_delay <= DAV1D_MAX_FRAME_DELAY, DAV1D_ERR(EINVAL));
+
+    get_num_threads(NULL, s, &n_tc, &n_fc);
+    return n_fc;
+}
+
 COLD int dav1d_open(Dav1dContext **const c_out, const Dav1dSettings *const s) {
     static pthread_once_t initted = PTHREAD_ONCE_INIT;
     pthread_once(&initted, init_internal);