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typefindfunctions: Implement better & more flexible MPEG4 typefinding
This detects more MPEG4 streams as MPEG4. Fixes bug #556537.
This commit is contained in:
Arnout Vandecappelle
Sebastian Dröge
parent
713f6ca8d5
commit
ce24ac4ed0
1 changed files with 138 additions and 36 deletions
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@ -1648,47 +1648,152 @@ mpeg_ts_type_find (GstTypeFind * tf, gpointer unused)
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}
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}
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#define GST_MPEGVID_TYPEFIND_TRY_PICTURES 6
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#define GST_MPEGVID_TYPEFIND_TRY_SYNC (100 * 1024) /* 100 kB */
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/**
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* Scan ahead a maximum of max_extra_offset bytes until the next IS_MPEG_HEADER
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* offset. After the call, offset will be after the 0x000001, i.e. at the 4th
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* byte of the MPEG header. Returns TRUE if a header was found, FALSE if not.
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*/
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static gboolean
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mpeg_find_next_header (GstTypeFind * tf, DataScanCtx * c,
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guint64 max_extra_offset)
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{
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guint64 extra_offset;
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for (extra_offset = 0; extra_offset <= max_extra_offset; ++extra_offset) {
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if (!data_scan_ctx_ensure_data (tf, c, 4))
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return FALSE;
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if (IS_MPEG_HEADER (c->data)) {
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data_scan_ctx_advance (tf, c, 3);
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return TRUE;
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}
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data_scan_ctx_advance (tf, c, 1);
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}
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return FALSE;
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}
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/*** video/mpeg MPEG-4 elementary video stream ***/
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static GstStaticCaps mpeg4_video_caps = GST_STATIC_CAPS ("video/mpeg, "
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"systemstream = (boolean) false, mpegversion = 4");
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#define MPEG4_VIDEO_CAPS gst_static_caps_get(&mpeg4_video_caps)
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/*
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* This typefind is based on the elementary video header defined in
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* http://xhelmboyx.tripod.com/formats/mpeg-layout.txt
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* In addition, it allows the visual object sequence header to be
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* absent, and even the VOS header to be absent. In the latter case,
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* a number of VOPs have to be present.
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*/
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static void
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mpeg4_video_type_find (GstTypeFind * tf, gpointer unused)
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{
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/* Header consists of: a series of start codes (00 00 01 xx), some with
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* associated data.
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* Optionally, we start with a visual_object_sequence_start_code, followed by
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* (optionally) visual_object_start_code), then the mandatory
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* video_object_start_code and video_object_layer_start_code)
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*/
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guint8 *data = NULL;
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int offset = 0;
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DataScanCtx c = { 0, NULL, 0 };
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gboolean seen_vios_at_0 = FALSE;
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gboolean seen_vios = FALSE;
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gboolean seen_vos = FALSE;
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gboolean seen_vol = FALSE;
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guint num_vop_headers = 0;
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guint8 sc;
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while (TRUE) {
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data = gst_type_find_peek (tf, offset, 4);
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if (data && IS_MPEG_HEADER (data)) {
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int sc = data[3];
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while (c.offset < GST_MPEGVID_TYPEFIND_TRY_SYNC) {
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if (num_vop_headers >= GST_MPEGVID_TYPEFIND_TRY_PICTURES)
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break;
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if (sc == 0xB0) /* visual_object_sequence_start_code */
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offset += 5;
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else if (sc == 0xB5) /* visual_object_start_code */
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offset += 5;
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else if (sc >= 0x00 && sc <= 0x1F) { /* video_object_start_code */
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offset += 4;
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seen_vos = TRUE;
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} else if (sc >= 0x20 && sc <= 0x2F) { /* video_object_layer_start_code */
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if (seen_vos) {
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gst_type_find_suggest (tf, GST_TYPE_FIND_NEARLY_CERTAIN,
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MPEG4_VIDEO_CAPS);
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return;
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} else
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return;
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} else
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return;
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} else
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return;
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if (!mpeg_find_next_header (tf, &c,
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GST_MPEGVID_TYPEFIND_TRY_SYNC - c.offset))
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break;
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sc = c.data[0];
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/* visual_object_sequence_start_code */
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if (sc == 0xB0) {
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if (seen_vios)
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break; /* Terminate at second vios */
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if (c.offset == 0)
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seen_vios_at_0 = TRUE;
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seen_vios = TRUE;
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data_scan_ctx_advance (tf, &c, 2);
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if (!mpeg_find_next_header (tf, &c, 0))
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break;
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sc = c.data[0];
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/* Optional metadata */
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if (sc == 0xB2)
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if (!mpeg_find_next_header (tf, &c, 24))
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break;
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}
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/* visual_object_start_code (consider it optional) */
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if (sc == 0xB5) {
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data_scan_ctx_advance (tf, &c, 2);
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/* may contain ID marker and YUV clamping */
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if (!mpeg_find_next_header (tf, &c, 7))
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break;
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sc = c.data[0];
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}
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/* video_object_start_code */
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if (sc <= 0x1F) {
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if (seen_vos)
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break; /* Terminate at second vos */
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seen_vos = TRUE;
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data_scan_ctx_advance (tf, &c, 2);
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continue;
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}
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/* video_object_layer_start_code */
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if (sc >= 0x20 && sc <= 0x2F) {
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seen_vol = TRUE;
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data_scan_ctx_advance (tf, &c, 5);
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continue;
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}
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/* video_object_plane_start_code */
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if (sc == 0xB6) {
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num_vop_headers++;
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data_scan_ctx_advance (tf, &c, 2);
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continue;
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}
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/* Unknown start code. */
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}
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if (num_vop_headers > 0 || seen_vol) {
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GstTypeFindProbability probability = 0;
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GST_LOG ("Found %d pictures, vios: %d, vos:%d, vol:%d", num_vop_headers,
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seen_vios, seen_vos, seen_vol);
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if (num_vop_headers >= GST_MPEGVID_TYPEFIND_TRY_PICTURES && seen_vios_at_0
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&& seen_vos && seen_vol)
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probability = GST_TYPE_FIND_MAXIMUM - 1;
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else if (num_vop_headers >= GST_MPEGVID_TYPEFIND_TRY_PICTURES && seen_vios
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&& seen_vos && seen_vol)
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probability = GST_TYPE_FIND_NEARLY_CERTAIN - 1;
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else if (seen_vios_at_0 && seen_vos && seen_vol)
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probability = GST_TYPE_FIND_NEARLY_CERTAIN - 6;
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else if (num_vop_headers >= GST_MPEGVID_TYPEFIND_TRY_PICTURES && seen_vos
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&& seen_vol)
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probability = GST_TYPE_FIND_NEARLY_CERTAIN - 6;
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else if (num_vop_headers >= GST_MPEGVID_TYPEFIND_TRY_PICTURES && seen_vol)
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probability = GST_TYPE_FIND_NEARLY_CERTAIN - 9;
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else if (num_vop_headers >= GST_MPEGVID_TYPEFIND_TRY_PICTURES)
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probability = GST_TYPE_FIND_LIKELY - 1;
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else if (num_vop_headers > 2 && seen_vios && seen_vos && seen_vol)
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probability = GST_TYPE_FIND_LIKELY - 9;
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else if (seen_vios && seen_vos && seen_vol)
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probability = GST_TYPE_FIND_LIKELY - 20;
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else if (num_vop_headers > 0 && seen_vos && seen_vol)
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probability = GST_TYPE_FIND_POSSIBLE;
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else if (num_vop_headers > 0)
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probability = GST_TYPE_FIND_POSSIBLE - 10;
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else if (seen_vos && seen_vol)
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probability = GST_TYPE_FIND_POSSIBLE - 20;
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gst_type_find_suggest_simple (tf, probability, "video/mpeg",
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"systemstream", G_TYPE_BOOLEAN, FALSE,
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"mpegversion", G_TYPE_INT, 4, NULL);
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}
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}
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@ -1772,9 +1877,6 @@ static GstStaticCaps mpeg_video_caps = GST_STATIC_CAPS ("video/mpeg, "
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* I'm sure someone will do a chance calculation here too.
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*/
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#define GST_MPEGVID_TYPEFIND_TRY_PICTURES 6
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#define GST_MPEGVID_TYPEFIND_TRY_SYNC (100 * 1024) /* 100 kB */
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static void
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mpeg_video_stream_type_find (GstTypeFind * tf, gpointer unused)
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{
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