avformat/dvdvideodec: implement seeking

Player applications can now enjoy seeking while playing back
a title. Accuracy is at the mercy of what libdvdnav exposes,
which is currently dvdnav_time_search().

Signed-off-by: Marth64 <marth64@proxyid.net>
Signed-off-by: Anton Khirnov <anton@khirnov.net>

libavformat/dvdvideodec.c

@@ -110,6 +110,7 @@ typedef struct DVDVideoPlaybackState {
     int                         in_pgc;             /* if our navigator is in the PGC */
     int                         in_ps;              /* if our navigator is in the program stream */
     int                         in_vts;             /* if our navigator is in the VTS */
+    int                         is_seeking;         /* relax navigation path while seeking */
     int64_t                     nav_pts;            /* PTS according to IFO, not frame-accurate */
     uint64_t                    pgc_duration_est;   /* estimated duration as reported by IFO */
     uint64_t                    pgc_elapsed;        /* the elapsed time of the PGC, cell-relative */
@@ -167,6 +168,7 @@ typedef struct DVDVideoDemuxContext {
     int                         play_end;           /* signal EOF to the parent demuxer */
     DVDVideoPlaybackState       play_state;         /* the active playback state */
     int                         play_started;       /* signal that playback has started */
+    int                         seek_warned;        /* signal that we warned about seeking limits */
     int                         segment_started;    /* signal that subdemuxer is on a segment */
 } DVDVideoDemuxContext;
 
@@ -715,7 +717,8 @@ static int dvdvideo_play_next_ps_block(AVFormatContext *s, DVDVideoPlaybackState
 
                         state->in_pgc = 1;
                     }
-                } else if (state->celln >= e_cell->cellN || state->pgn > cur_pgn) {
+                } else if (!state->is_seeking &&
+                           (state->celln >= e_cell->cellN || state->pgn > cur_pgn)) {
                     return AVERROR_EOF;
                 }
 
@@ -728,7 +731,7 @@ static int dvdvideo_play_next_ps_block(AVFormatContext *s, DVDVideoPlaybackState
                 if (!state->in_pgc)
                     continue;
 
-                if ((state->ptt > 0 && state->ptt > cur_ptt) ||
+                if ((!state->is_seeking && state->ptt > 0 && state->ptt > cur_ptt) ||
                     (c->opt_chapter_end > 0 && cur_ptt > c->opt_chapter_end)) {
                     return AVERROR_EOF;
                 }
@@ -811,6 +814,8 @@ static int dvdvideo_play_next_ps_block(AVFormatContext *s, DVDVideoPlaybackState
 
                 (*p_nav_event) = nav_event;
 
+                state->is_seeking = 0;
+
                 return nav_len;
             case DVDNAV_WAIT:
                 if (dvdnav_wait_skip(state->dvdnav) != DVDNAV_STATUS_OK) {
@@ -1688,6 +1693,67 @@ static int dvdvideo_close(AVFormatContext *s)
     return 0;
 }
 
+static int dvdvideo_read_seek(AVFormatContext *s, int stream_index, int64_t timestamp, int flags)
+{
+    DVDVideoDemuxContext *c = s->priv_data;
+    int64_t new_nav_pts;
+    pci_t*  new_nav_pci;
+    dsi_t*  new_nav_dsi;
+
+    if (c->opt_menu || c->opt_chapter_start > 1) {
+        av_log(s, AV_LOG_ERROR, "Seeking is not compatible with menus or chapter extraction\n");
+
+        return AVERROR_PATCHWELCOME;
+    }
+
+    if ((flags & AVSEEK_FLAG_BYTE))
+        return AVERROR(ENOSYS);
+
+    if (timestamp < 0)
+        return AVERROR(EINVAL);
+
+    if (!c->seek_warned) {
+        av_log(s, AV_LOG_WARNING, "Seeking is inherently unreliable and will result "
+                                  "in imprecise timecodes from this point\n");
+        c->seek_warned = 1;
+    }
+
+    /* XXX(PATCHWELCOME): use dvdnav_jump_to_sector_by_time(c->play_state.dvdnav, timestamp, 0)
+     * when it is available in a released version of libdvdnav; it is more accurate */
+    if (dvdnav_time_search(c->play_state.dvdnav, timestamp) != DVDNAV_STATUS_OK) {
+        av_log(s, AV_LOG_ERROR, "libdvdnav: seeking to %" PRId64 " failed\n", timestamp);
+
+        return AVERROR_EXTERNAL;
+    }
+
+    new_nav_pts = dvdnav_get_current_time   (c->play_state.dvdnav);
+    new_nav_pci = dvdnav_get_current_nav_pci(c->play_state.dvdnav);
+    new_nav_dsi = dvdnav_get_current_nav_dsi(c->play_state.dvdnav);
+
+    if (new_nav_pci == NULL || new_nav_dsi == NULL) {
+        av_log(s, AV_LOG_ERROR, "Invalid NAV packet after seeking\n");
+
+        return AVERROR_INVALIDDATA;
+    }
+
+    c->play_state.in_pgc      = 1;
+    c->play_state.in_ps       = 0;
+    c->play_state.is_seeking  = 1;
+    c->play_state.nav_pts     = timestamp;
+    c->play_state.ts_offset   = timestamp;
+    c->play_state.vobu_e_ptm  = new_nav_pci->pci_gi.vobu_s_ptm;
+
+    c->first_pts              = 0;
+    c->play_started           = 0;
+
+    dvdvideo_subdemux_flush(s);
+
+    av_log(s, AV_LOG_DEBUG, "seeking: requested_nav_pts=%" PRId64 " new_nav_pts=%" PRId64 "\n",
+                            timestamp, new_nav_pts);
+
+    return 0;
+}
+
 #define OFFSET(x) offsetof(DVDVideoDemuxContext, x)
 static const AVOption dvdvideo_options[] = {
     {"angle",           "playback angle number",                                    OFFSET(opt_angle),          AV_OPT_TYPE_INT,    { .i64=1 },     1,          9,         AV_OPT_FLAG_DECODING_PARAM },
@@ -1716,11 +1782,12 @@ const FFInputFormat ff_dvdvideo_demuxer = {
     .p.name         = "dvdvideo",
     .p.long_name    = NULL_IF_CONFIG_SMALL("DVD-Video"),
     .p.priv_class   = &dvdvideo_class,
-    .p.flags        = AVFMT_NOFILE | AVFMT_SHOW_IDS | AVFMT_TS_DISCONT |
-                      AVFMT_NO_BYTE_SEEK | AVFMT_NOGENSEARCH | AVFMT_NOBINSEARCH,
+    .p.flags        = AVFMT_SHOW_IDS | AVFMT_TS_DISCONT   | AVFMT_SEEK_TO_PTS |
+                      AVFMT_NOFILE   | AVFMT_NO_BYTE_SEEK | AVFMT_NOGENSEARCH | AVFMT_NOBINSEARCH,
     .priv_data_size = sizeof(DVDVideoDemuxContext),
     .flags_internal = FF_INFMT_FLAG_INIT_CLEANUP,
     .read_close     = dvdvideo_close,
     .read_header    = dvdvideo_read_header,
-    .read_packet    = dvdvideo_read_packet
+    .read_packet    = dvdvideo_read_packet,
+    .read_seek      = dvdvideo_read_seek
 };