[FFmpeg-devel] [PATCH 05/28] support seeking in nuv files

[Mans Rullgard]

From: Cory Fields <theuni-nospam- at xbmc.org>

---
 libavformat/nuv.c |   84 +++++++++++++++++++++++++++++++++++++++++++++++++++++
 1 files changed, 84 insertions(+), 0 deletions(-)

diff --git a/libavformat/nuv.c b/libavformat/nuv.c
index f0eacd5..2aa0bb4 100644
--- a/libavformat/nuv.c
+++ b/libavformat/nuv.c
@@ -218,12 +218,18 @@ static int nuv_packet(AVFormatContext *s, AVPacket *pkt) {
                 ret = av_new_packet(pkt, copyhdrsize + size);
                 if (ret < 0)
                     return ret;
+
                 // HACK: we have no idea if it is a keyframe,
                 // but if we mark none seeking will not work at all.
                 pkt->flags |= AV_PKT_FLAG_KEY;
                 pkt->pos = pos;
                 pkt->pts = AV_RL32(&hdr[4]);
                 pkt->stream_index = ctx->v_id;
+                if(hdr[2] == 0) {
+                    AVStream *st = s->streams[pkt->stream_index];
+                    pkt->flags |= PKT_FLAG_KEY;
+                    av_add_index_entry(st, pkt->pos, pkt->pts, size + HDRSIZE, 0, AVINDEX_KEYFRAME);
+                }
                 memcpy(pkt->data, hdr, copyhdrsize);
                 ret = get_buffer(pb, pkt->data + copyhdrsize, size);
                 if (ret < 0) {
@@ -257,6 +263,83 @@ static int nuv_packet(AVFormatContext *s, AVPacket *pkt) {
     return AVERROR(EIO);
 }
 
+/**
+ * \brief looks for the string RTjjjjjjjjjj in the stream too resync reading
+ * \return TRUE if the syncword is found.
+ */
+static int nuv_resync(AVFormatContext *s, int64_t pos_limit) {
+    ByteIOContext *pb = s->pb;
+    uint32_t tag;
+
+    tag = get_be32(pb);
+    while(!url_feof(pb) && url_ftell(pb) < pos_limit) {
+        if(tag != MKBETAG('R','T','j','j')) {
+            tag = (tag << 8) | get_byte(pb);
+            continue;
+        }
+        tag = get_be32(pb);
+        if(tag != MKBETAG('j','j','j','j'))
+          continue;
+
+        tag = get_be32(pb);
+        if(tag != MKBETAG('j','j','j','j'))
+          continue;
+
+        return 1;
+    }
+    return 0;
+}
+
+/**
+ * \brief attempts to read a timestamp from stream at the given stream position
+ * \return timestamp if successfull and AV_NOPTS_VALUE if failure
+ */
+static int64_t nuv_read_dts(AVFormatContext *s, int stream_index,
+                               int64_t *ppos, int64_t pos_limit)
+{
+    NUVContext *ctx = s->priv_data;
+    ByteIOContext *pb = s->pb;
+    uint8_t hdr[HDRSIZE];
+    nuv_frametype frametype;
+    int size;
+    int64_t pos, dts;
+
+    if (url_fseek(pb, *ppos, SEEK_SET) < 0)
+        return AV_NOPTS_VALUE;
+
+    if (!nuv_resync(s, pos_limit))
+        return AV_NOPTS_VALUE;
+
+    while (!url_feof(pb) && url_ftell(pb) < pos_limit) {
+        if (get_buffer(pb, hdr, HDRSIZE) <= 0)
+            return AV_NOPTS_VALUE;
+        frametype = hdr[0];
+        size = PKTSIZE(AV_RL32(&hdr[8]));
+        switch (frametype) {
+            case NUV_SEEKP:
+                break;
+            case NUV_AUDIO:
+            case NUV_VIDEO:
+                pos = url_ftell(s->pb) - HDRSIZE;
+                dts = AV_RL32(&hdr[4]);
+                // TODO - add general support in av_gen_search, so it adds positions after reading timestamps
+                av_add_index_entry(s->streams[frametype == NUV_VIDEO ? ctx->v_id : ctx->a_id]
+                                 , pos, dts, size + HDRSIZE, 0, hdr[2] == 0 ? AVINDEX_KEYFRAME : 0);
+
+                if ((frametype == NUV_VIDEO && stream_index == ctx->v_id) ||
+                    (frametype == NUV_AUDIO && stream_index == ctx->a_id)) {
+                    *ppos = pos;
+                    return dts;
+                }
+            default:
+                url_fskip(pb, size);
+                break;
+        }
+    }
+    return AV_NOPTS_VALUE;
+}
+
+
 AVInputFormat nuv_demuxer = {
     "nuv",
     NULL_IF_CONFIG_SMALL("NuppelVideo format"),
@@ -266,5 +349,6 @@ AVInputFormat nuv_demuxer = {
     nuv_packet,
     NULL,
     NULL,
+    nuv_read_dts,
     .flags = AVFMT_GENERIC_INDEX,
 };
-- 
1.7.1.1