tests: qtdemux: add test for MSS fragment wrong data offset compensation

A data offset with an offset smaller than the moof length is wrong
in smooth streaming streams. The samples will not be located and
eventually playback will error out. So compensate assuming data
is in mdat following moof.

Part-of: <https://gitlab.freedesktop.org/gstreamer/gstreamer/-/merge_requests/3840>

subprojects/gst-plugins-good/tests/check/elements/qtdemux.c

@@ -988,6 +988,218 @@ GST_START_TEST (test_qtdemux_pad_names)
 
 GST_END_TEST;
 
+typedef struct
+{
+  GstPad *sinkpad;
+  guint sample_cnt;
+  guint expected_sample_cnt;
+} MssModeTestData;
+
+static GstPadProbeReturn
+qtdemux_probe_for_mss_mode (GstPad * pad, GstPadProbeInfo * info,
+    MssModeTestData * data)
+{
+  data->sample_cnt++;
+  GST_LOG ("samples received: %u", data->sample_cnt);
+  return GST_PAD_PROBE_OK;
+}
+
+static void
+qtdemux_pad_added_cb_in_mss_mode (GstElement * element, GstPad * pad,
+    MssModeTestData * data)
+{
+  GST_DEBUG_OBJECT (pad, "New pad added");
+
+  if (!data->sinkpad) {
+    GstPad *sinkpad = gst_pad_new_from_static_template (&sinktemplate, "sink");
+
+    gst_pad_set_event_function (sinkpad, _sink_event);
+    gst_pad_set_chain_function (sinkpad, _sink_chain);
+
+    gst_pad_add_probe (sinkpad, GST_PAD_PROBE_TYPE_BUFFER,
+        (GstPadProbeCallback) qtdemux_probe_for_mss_mode, data, NULL);
+    gst_pad_set_active (sinkpad, TRUE);
+    data->sinkpad = sinkpad;
+    gst_pad_link (pad, sinkpad);
+  }
+}
+
+/* Fragment taken from
+ * http://amssamples.streaming.mediaservices.windows.net/b6822ec8-5c2b-4ae0-a851-fd46a78294e9/ElephantsDream.ism/QualityLevels(53644)/Fragments(AAC_und_ch2_56kbps=0)
+ */
+#define MSS_FRAGMENT TEST_FILE_PREFIX "mss-fragment.m4f"
+static guint8 *mss_fragment;
+static const guint mss_fragment_len = 14400;
+
+GST_START_TEST (test_qtdemux_compensate_data_offset)
+{
+  /* Same fragment as above, but with modified trun box data offset field
+   * from 871 to 791 to mimic an mss fragment with data offset smaller
+   * than the moof size. */
+  const guint mss_fragment_wrong_data_offset_len = 14400;
+  guint8 *mss_fragment_wrong_data_offset;
+  GstElement *qtdemux;
+  GstPad *sinkpad;
+  GstBuffer *inbuf;
+  GstSegment segment;
+  GstEvent *event;
+  GstCaps *caps;
+  GstCaps *mediacaps;
+  MssModeTestData data = { 0, };
+
+  data.expected_sample_cnt = 87;
+
+  g_assert (load_file (MSS_FRAGMENT, &mss_fragment, mss_fragment_len));
+
+  /* Change trun box data offset field from 871 to 791 to mimic an MSS fragment
+   * with data offset smaller than the moof size. */
+  mss_fragment_wrong_data_offset = g_memdup2 (mss_fragment, mss_fragment_len);
+  g_assert (GST_READ_UINT32_BE (&mss_fragment_wrong_data_offset[64]) == 871);
+  GST_WRITE_UINT32_BE (&mss_fragment_wrong_data_offset[64], 791);
+
+  /* The goal of this test is to check that qtdemux can compensate
+   * wrong data offset in trun boxes and allow proper parsing of samples
+   * in mss mode.
+   */
+
+  qtdemux = gst_element_factory_make ("qtdemux", NULL);
+  gst_element_set_state (qtdemux, GST_STATE_PLAYING);
+  sinkpad = gst_element_get_static_pad (qtdemux, "sink");
+
+  /* We'll want to know when the source pad is added */
+  g_signal_connect (qtdemux, "pad-added", (GCallback)
+      qtdemux_pad_added_cb_in_mss_mode, &data);
+
+  /* Send the initial STREAM_START and segment (TIME) event */
+  event = gst_event_new_stream_start ("TEST");
+  GST_DEBUG ("Pushing stream-start event");
+  fail_unless (gst_pad_send_event (sinkpad, event) == TRUE);
+
+  /* Send CAPS event* */
+  mediacaps = gst_caps_new_simple ("audio/mpeg",
+      "mpegversion", G_TYPE_INT, 4,
+      "channels", G_TYPE_INT, 2, "rate", G_TYPE_INT, 48000, NULL);
+  caps =
+      gst_caps_new_simple ("video/quicktime", "variant", G_TYPE_STRING,
+      "mss-fragmented", "timescale", G_TYPE_UINT64, 10000000, "media-caps",
+      GST_TYPE_CAPS, mediacaps, NULL);
+
+  /* Send segment event* */
+  event = gst_event_new_caps (caps);
+  GST_DEBUG ("Pushing caps event");
+  fail_unless (gst_pad_send_event (sinkpad, event) == TRUE);
+  gst_caps_unref (mediacaps);
+  gst_caps_unref (caps);
+
+  gst_segment_init (&segment, GST_FORMAT_TIME);
+  event = gst_event_new_segment (&segment);
+  GST_DEBUG ("Pushing segment event");
+  fail_unless (gst_pad_send_event (sinkpad, event) == TRUE);
+
+  /* Send the first fragment */
+  /* NOTE: mss streams don't have moov */
+  inbuf = gst_buffer_new_and_alloc (mss_fragment_wrong_data_offset_len);
+  gst_buffer_fill (inbuf, 0, mss_fragment_wrong_data_offset,
+      mss_fragment_wrong_data_offset_len);
+  GST_BUFFER_PTS (inbuf) = 0;
+  GST_BUFFER_OFFSET (inbuf) = 0;
+  GST_BUFFER_FLAG_SET (inbuf, GST_BUFFER_FLAG_DISCONT);
+  GST_DEBUG ("Pushing fragment");
+  fail_unless (gst_pad_chain (sinkpad, inbuf) == GST_FLOW_OK);
+  fail_if (data.sinkpad == NULL);
+
+  /* If data offset has been compensated samples will be pushed as normal */
+  fail_unless (data.sample_cnt == data.expected_sample_cnt);
+
+  gst_object_unref (sinkpad);
+  gst_pad_set_active (data.sinkpad, FALSE);
+  gst_object_unref (data.sinkpad);
+  gst_element_set_state (qtdemux, GST_STATE_NULL);
+  gst_object_unref (qtdemux);
+
+  g_free (mss_fragment_wrong_data_offset);
+  g_clear_pointer (&mss_fragment, (GDestroyNotify) g_free);
+}
+
+GST_END_TEST;
+
+GST_START_TEST (test_qtdemux_mss_fragment)
+{
+  GstElement *qtdemux;
+  GstPad *sinkpad;
+  GstBuffer *inbuf;
+  GstSegment segment;
+  GstEvent *event;
+  GstCaps *caps;
+  GstCaps *mediacaps;
+  MssModeTestData data = { 0, };
+
+  data.expected_sample_cnt = 87;
+
+  g_assert (load_file (MSS_FRAGMENT, &mss_fragment, mss_fragment_len));
+
+  /* The goal of this test is to check that qtdemux can handle a normal
+   * mss fragment.
+   */
+
+  qtdemux = gst_element_factory_make ("qtdemux", NULL);
+  gst_element_set_state (qtdemux, GST_STATE_PLAYING);
+  sinkpad = gst_element_get_static_pad (qtdemux, "sink");
+
+  /* We'll want to know when the source pad is added */
+  g_signal_connect (qtdemux, "pad-added", (GCallback)
+      qtdemux_pad_added_cb_in_mss_mode, &data);
+
+  /* Send the initial STREAM_START and segment (TIME) event */
+  event = gst_event_new_stream_start ("TEST");
+  GST_DEBUG ("Pushing stream-start event");
+  fail_unless (gst_pad_send_event (sinkpad, event) == TRUE);
+
+  /* Send CAPS event* */
+  mediacaps = gst_caps_new_simple ("audio/mpeg",
+      "mpegversion", G_TYPE_INT, 4,
+      "channels", G_TYPE_INT, 2, "rate", G_TYPE_INT, 48000, NULL);
+  caps =
+      gst_caps_new_simple ("video/quicktime", "variant", G_TYPE_STRING,
+      "mss-fragmented", "timescale", G_TYPE_UINT64, 10000000, "media-caps",
+      GST_TYPE_CAPS, mediacaps, NULL);
+
+  /* Send segment event* */
+  event = gst_event_new_caps (caps);
+  GST_DEBUG ("Pushing caps event");
+  fail_unless (gst_pad_send_event (sinkpad, event) == TRUE);
+  gst_caps_unref (mediacaps);
+  gst_caps_unref (caps);
+
+  gst_segment_init (&segment, GST_FORMAT_TIME);
+  event = gst_event_new_segment (&segment);
+  GST_DEBUG ("Pushing segment event");
+  fail_unless (gst_pad_send_event (sinkpad, event) == TRUE);
+
+  /* Send the first fragment */
+  /* NOTE: mss streams don't have moov */
+  inbuf = gst_buffer_new_and_alloc (mss_fragment_len);
+  gst_buffer_fill (inbuf, 0, mss_fragment, mss_fragment_len);
+  GST_BUFFER_PTS (inbuf) = 0;
+  GST_BUFFER_OFFSET (inbuf) = 0;
+  GST_BUFFER_FLAG_SET (inbuf, GST_BUFFER_FLAG_DISCONT);
+  GST_DEBUG ("Pushing fragment");
+  fail_unless (gst_pad_chain (sinkpad, inbuf) == GST_FLOW_OK);
+  fail_if (data.sinkpad == NULL);
+
+  fail_unless (data.sample_cnt == data.expected_sample_cnt);
+
+  gst_object_unref (sinkpad);
+  gst_pad_set_active (data.sinkpad, FALSE);
+  gst_object_unref (data.sinkpad);
+  gst_element_set_state (qtdemux, GST_STATE_NULL);
+  gst_object_unref (qtdemux);
+
+  g_clear_pointer (&mss_fragment, (GDestroyNotify) g_free);
+}
+
+GST_END_TEST;
+
 static Suite *
 qtdemux_suite (void)
 {
@@ -1001,6 +1213,8 @@ qtdemux_suite (void)
   tcase_add_test (tc_chain, test_qtdemux_duplicated_moov);
   tcase_add_test (tc_chain, test_qtdemux_stream_change);
   tcase_add_test (tc_chain, test_qtdemux_pad_names);
+  tcase_add_test (tc_chain, test_qtdemux_compensate_data_offset);
+  tcase_add_test (tc_chain, test_qtdemux_mss_fragment);
 
   return s;
 }