seek support

Originally committed as revision 2501 to svn://svn.ffmpeg.org/ffmpeg/trunk

libavformat/mpegts.c

@@ -21,6 +21,7 @@
 #include "mpegts.h"
 
 //#define DEBUG_SI
+//#define DEBUG_SEEK
 
 /* 1.0 second at 24Mbit/s */
 #define MAX_SCAN_PACKETS 32000
@@ -87,6 +88,7 @@ struct MpegTSContext {
     /* used to estimate the exact PCR */
     int64_t cur_pcr;
     int pcr_incr;
+    int pcr_pid;
     
     /* data needed to handle file based ts */
     int stop_parse; /* stop parsing loop */
@@ -367,6 +369,7 @@ static void pmt_cb(void *opaque, const uint8_t *section, int section_len)
     pcr_pid = get16(&p, p_end) & 0x1fff;
     if (pcr_pid < 0)
         return;
+    ts->pcr_pid = pcr_pid;
 #ifdef DEBUG_SI
     printf("pcr_pid=0x%x\n", pcr_pid);
 #endif
@@ -710,6 +713,7 @@ static void mpegts_push_data(void *opaque,
                             st->priv_data = pes;
                             st->codec.codec_type = codec_type;
                             st->codec.codec_id = codec_id;
+                            st->need_parsing = 1;
                             pes->st = st;
                         }
                     }
@@ -1117,6 +1121,7 @@ static int mpegts_read_header(AVFormatContext *s,
             }
             nb_packets++;
         }
+        ts->pcr_pid = pcr_pid;
 
         /* NOTE1: the bitrate is computed without the FEC */
         /* NOTE2: it is only the bitrate of the start of the stream */
@@ -1204,6 +1209,156 @@ static int mpegts_read_close(AVFormatContext *s)
     return 0;
 }
 
+static int64_t mpegts_get_pcr(AVFormatContext *s, int stream_index, 
+                              int64_t *ppos, int find_next)
+{
+    MpegTSContext *ts = s->priv_data;
+    int64_t pos, timestamp;
+    uint8_t buf[TS_PACKET_SIZE];
+    int pcr_l, pid;
+
+    pos = *ppos;
+    if (find_next) {
+        for(;;) {
+            url_fseek(&s->pb, pos, SEEK_SET);
+            if (get_buffer(&s->pb, buf, TS_PACKET_SIZE) != TS_PACKET_SIZE)
+                return AV_NOPTS_VALUE;
+            pid = ((buf[1] & 0x1f) << 8) | buf[2];
+            if (pid == ts->pcr_pid &&
+                parse_pcr(&timestamp, &pcr_l, buf) == 0) {
+                break;
+            }
+            pos += ts->raw_packet_size;
+        }
+    } else {
+        for(;;) {
+            pos -= ts->raw_packet_size;
+            if (pos < 0)
+                return AV_NOPTS_VALUE;
+            url_fseek(&s->pb, pos, SEEK_SET);
+            if (get_buffer(&s->pb, buf, TS_PACKET_SIZE) != TS_PACKET_SIZE)
+                return AV_NOPTS_VALUE;
+            pid = ((buf[1] & 0x1f) << 8) | buf[2];
+            if (pid == ts->pcr_pid &&
+                parse_pcr(&timestamp, &pcr_l, buf) == 0) {
+                break;
+            }
+        }
+    }
+    *ppos = pos;
+    return timestamp;
+}
+
+typedef int64_t ReadTimestampFunc(AVFormatContext *s, int stream_index, 
+                                  int64_t *ppos, int find_next);
+
+static int64_t do_block_align(int64_t val, int block_align)
+{
+    return (val / block_align) * block_align;
+}
+
+/* XXX: use it in other formats */
+static int timestamp_read_seek(AVFormatContext *s, 
+                               int stream_index, int64_t timestamp,
+                               ReadTimestampFunc *read_timestamp,
+                               int block_align)
+{
+    int64_t pos_min, pos_max, pos;
+    int64_t dts_min, dts_max, dts;
+
+#ifdef DEBUG_SEEK
+    printf("read_seek: %d %0.3f\n", stream_index, timestamp / 90000.0);
+#endif
+
+    pos_min = 0;
+    dts_min = read_timestamp(s, stream_index, &pos_min, 1);
+    if (dts_min == AV_NOPTS_VALUE) {
+        /* we can reach this case only if no PTS are present in
+           the whole stream */
+        return -1;
+    }
+    pos_max = do_block_align(url_filesize(url_fileno(&s->pb)), block_align) - 
+        block_align;
+    dts_max = read_timestamp(s, stream_index, &pos_max, 0);
+    
+    while (pos_min <= pos_max) {
+#ifdef DEBUG_SEEK
+        printf("pos_min=0x%llx pos_max=0x%llx dts_min=%0.3f dts_max=%0.3f\n", 
+               pos_min, pos_max,
+               dts_min / 90000.0, dts_max / 90000.0);
+#endif
+        if (timestamp <= dts_min) {
+            pos = pos_min;
+            goto found;
+        } else if (timestamp >= dts_max) {
+            pos = pos_max;
+            goto found;
+        } else {
+            /* interpolate position (better than dichotomy) */
+            pos = (int64_t)((double)(pos_max - pos_min) * 
+                            (double)(timestamp - dts_min) /
+                            (double)(dts_max - dts_min)) + pos_min;
+            pos = do_block_align(pos, block_align);
+        }
+#ifdef DEBUG_SEEK
+        printf("pos=0x%llx\n", pos);
+#endif
+        /* read the next timestamp */
+        dts = read_timestamp(s, stream_index, &pos, 1);
+        /* check if we are lucky */
+        if (dts == AV_NOPTS_VALUE) {
+            /* should never happen */
+            pos = pos_min;
+            goto found;
+        } else if (timestamp == dts) {
+            goto found;
+        } else if (timestamp < dts) {
+            pos_max = pos;
+            dts_max = read_timestamp(s, stream_index, &pos_max, 0);
+            if (dts_max == AV_NOPTS_VALUE) {
+                /* should never happen */
+                break;
+            } else if (timestamp >= dts_max) {
+                pos = pos_max;
+                goto found;
+            }
+        } else {
+            pos_min = pos + block_align;
+            dts_min = read_timestamp(s, stream_index, &pos_min, 1);
+            if (dts_min == AV_NOPTS_VALUE) {
+                /* should never happen */
+                goto found;
+            } else if (timestamp <= dts_min) {
+                goto found;
+            }
+        }
+    }
+    pos = pos_min;
+ found:
+#ifdef DEBUG_SEEK
+    pos_min = pos;
+    dts_min = read_timestamp(s, stream_index, &pos_min, 1);
+    pos_min += block_align;
+    dts_max = read_timestamp(s, stream_index, &pos_min, 1);
+    printf("pos=0x%llx %0.3f<=%0.3f<=%0.3f\n", 
+           pos, dts_min / 90000.0, timestamp / 90000.0, dts_max / 90000.0);
+#endif
+    /* do the seek */
+    url_fseek(&s->pb, pos, SEEK_SET);
+    return 0;
+}
+
+static int mpegts_read_seek(AVFormatContext *s, 
+                            int stream_index, int64_t timestamp)
+{
+    MpegTSContext *ts = s->priv_data;
+
+    timestamp = (timestamp * 90000) / AV_TIME_BASE;
+
+    return timestamp_read_seek(s, stream_index, timestamp, 
+                               mpegts_get_pcr, ts->raw_packet_size);
+}
+
 /**************************************************************/
 /* parsing functions - called from other demuxers such as RTP */
 
@@ -1265,6 +1420,7 @@ AVInputFormat mpegts_demux = {
     mpegts_read_header,
     mpegts_read_packet,
     mpegts_read_close,
+    mpegts_read_seek,
     .flags = AVFMT_SHOW_IDS,
 };