avidemux: fix offset handling in push mode seeking

Push mode seeking uses same index data as pull mode, and stores
offset to data in chunk, whereas push mode operates in chunks,
and as such needs offset consistently corresponding to chunk headers.
Also fix determining best matching stream for incoming newsegment event,
as well as setting some stream state accordingly.

gst/avi/gstavidemux.c

@@ -693,11 +693,14 @@ gst_avi_demux_seek_streams_index (GstAviDemux * avi, guint64 offset,
   for (i = 0; i < avi->num_streams; i++) {
     stream = &avi->stream[i];
 
+    /* compensate for chunk header */
+    offset += 8;
     entry =
         gst_util_array_binary_search (stream->index, stream->idx_n,
         sizeof (GstAviIndexEntry),
         (GCompareDataFunc) gst_avi_demux_index_entry_offset_search,
         before ? GST_SEARCH_MODE_BEFORE : GST_SEARCH_MODE_AFTER, &offset, NULL);
+    offset -= 8;
 
     if (entry)
       index = entry - stream->index;
@@ -720,13 +723,11 @@ gst_avi_demux_seek_streams_index (GstAviDemux * avi, guint64 offset,
       continue;
     }
 
-    val = stream->index[index].offset;
+    val = stream->index[index].offset - 8;
     GST_DEBUG_OBJECT (avi, "stream %d, next entry at %" G_GUINT64_FORMAT, i,
         val);
 
-    gst_avi_demux_get_buffer_info (avi, stream, index, (GstClockTime *) & val,
+    stream->current_total = stream->index[index].total;
-        NULL, NULL, NULL);
-    stream->current_total = val;
     stream->current_entry = index;
   }
 
@@ -777,9 +778,11 @@ gst_avi_demux_handle_sink_event (GstPad * pad, GstEvent * event)
 
       if (avi->have_index) {
         GstAviIndexEntry *entry;
-        guint i = 0, index;
+        guint i = 0, index = 0, k = 0;
         GstAviStream *stream;
 
+        /* compensate chunk header, stored index offset points after header */
+        start += 8;
         /* find which stream we're on */
         do {
           stream = &avi->stream[i];
@@ -788,17 +791,30 @@ gst_avi_demux_handle_sink_event (GstPad * pad, GstEvent * event)
           entry = gst_util_array_binary_search (stream->index,
               stream->idx_n, sizeof (GstAviIndexEntry),
               (GCompareDataFunc) gst_avi_demux_index_entry_offset_search,
-              GST_SEARCH_MODE_BEFORE, &start, NULL);
+              GST_SEARCH_MODE_AFTER, &start, NULL);
 
-          if (entry == NULL) {
+          if (entry == NULL)
-            index = 0;
+            continue;
-          } else {
           index = entry - stream->index;
-          }
 
+          /* we are on the stream with a chunk start offset closest to start */
+          if (!offset || stream->index[index].offset < offset) {
+            offset = stream->index[index].offset;
+            k = i;
+          }
+          /* exact match needs no further searching */
           if (stream->index[index].offset == start)
             break;
         } while (++i < avi->num_streams);
+        start -= 8;
+        offset -= 8;
+        stream = &avi->stream[k];
+
+        /* so we have no idea what is to come, or where we are */
+        if (!offset) {
+          GST_WARNING_OBJECT (avi, "insufficient index data, forcing EOS");
+          goto eos;
+        }
 
         /* get the ts corresponding to start offset bytes for the stream */
         gst_avi_demux_get_buffer_info (avi, stream, index,
@@ -818,13 +834,12 @@ gst_avi_demux_handle_sink_event (GstPad * pad, GstEvent * event)
         }
 
         gst_index_entry_assoc_map (entry, GST_FORMAT_TIME, &time);
-        gst_index_entry_assoc_map (entry, GST_FORMAT_BYTES, &start);
+        gst_index_entry_assoc_map (entry, GST_FORMAT_BYTES, &offset);
       } else {
         GST_WARNING_OBJECT (avi, "no index data, forcing EOS");
         goto eos;
       }
 
-      offset = start;
       stop = GST_CLOCK_TIME_NONE;
 
       /* set up segment and send downstream */
@@ -841,15 +856,15 @@ gst_avi_demux_handle_sink_event (GstPad * pad, GstEvent * event)
       GST_DEBUG_OBJECT (avi, "next chunk expected at %" G_GINT64_FORMAT, start);
 
       /* adjust state for streaming thread accordingly */
-      avi->offset = offset;
       if (avi->have_index)
         gst_avi_demux_seek_streams_index (avi, offset, FALSE);
       else
         gst_avi_demux_seek_streams (avi, offset, FALSE);
 
       /* set up streaming thread */
-      avi->offset = offset;
+      g_assert (offset >= start);
-      avi->todrop = start - offset;
+      avi->offset = start;
+      avi->todrop = offset - start;
 
     exit:
       gst_event_unref (event);
@@ -4190,7 +4205,8 @@ avi_demux_handle_seek_push (GstAviDemux * avi, GstPad * pad, GstEvent * event)
   /* re-use cur to be the timestamp of the seek as it _will_ be */
   cur = stream->current_timestamp;
 
-  min_offset = avi->seek_kf_offset = stream->index[index].offset;
+  min_offset = stream->index[index].offset;
+  avi->seek_kf_offset = min_offset - 8;
 
   GST_DEBUG_OBJECT (avi,
       "Seek to: ts %" GST_TIME_FORMAT " (on str %u, idx %u, offset %"
@@ -4241,8 +4257,12 @@ avi_demux_handle_seek_push (GstAviDemux * avi, GstPad * pad, GstEvent * event)
       GST_TIME_ARGS (stream->current_ts_end), stream->current_offset,
       stream->current_offset_end);
 
-  if (!perform_seek_to_offset (avi,
+  /* index data refers to data, not chunk header (for pull mode convenience) */
-          min_offset - (avi->stream[0].indexes ? 8 : 0))) {
+  min_offset -= 8;
+  GST_DEBUG_OBJECT (avi, "seeking to chunk at offset %" G_GUINT64_FORMAT,
+      min_offset);
+
+  if (!perform_seek_to_offset (avi, min_offset)) {
     GST_DEBUG_OBJECT (avi, "seek event failed!");
     return FALSE;
   }