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gst/qtdemux/qtdemux.c: Fix segment-stop regression.

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Original commit message from CVS:
* gst/qtdemux/qtdemux.c: (gst_qtdemux_activate_segment):
Fix segment-stop regression.
Add documentation regarding segments in quicktime files by Wim Taymans.
Fixes #544509
This commit is contained in:
Edward Hervey 2008-07-25 14:50:03 +00:00
parent f47d7b4809
commit 637854d725
2 changed files with 78 additions and 1 deletions
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7
ChangeLog
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@ -1,3 +1,10 @@
2008-07-25 Edward Hervey <edward.hervey@collabora.co.uk>
* gst/qtdemux/qtdemux.c: (gst_qtdemux_activate_segment):
Fix segment-stop regression.
Add documentation regarding segments in quicktime files by Wim Taymans.
Fixes #544509
2008-07-25 Jan Schmidt <jan.schmidt@sun.com>
* configure.ac:

72
gst/qtdemux/qtdemux.c
View file

@ -97,6 +97,64 @@ struct _QtDemuxSample
gboolean keyframe; /* TRUE when this packet is a keyframe */
};
/*
* Quicktime has tracks and segments. A track is a continuous piece of
* multimedia content. The track is not always played from start to finish but
* instead, pieces of the track are 'cut out' and played in sequence. This is
* what the segments do.
*
* Inside the track we have keyframes (K) and delta frames. The track has its
* own timing, which starts from 0 and extends to end. The position in the track
* is called the media_time.
*
* The segments now describe the pieces that should be played from this track
* and are basically tupples of media_time/duration/rate entries. We can have
* multiple segments and they are all played after one another. An example:
*
* segment 1: media_time: 1 second, duration: 1 second, rate 1
* segment 2: media_time: 3 second, duration: 2 second, rate 2
*
* To correctly play back this track, one must play: 1 second of media starting
* from media_time 1 followed by 2 seconds of media starting from media_time 3
* at a rate of 2.
*
* Each of the segments will be played at a specific time, the first segment at
* time 0, the second one after the duration of the first one, etc.. Note that
* the time in resulting playback is not identical to the media_time of the
* track anymore.
*
* Visually, assuming the track has 4 second of media_time:
*
* (a) (b) (c) (d)
* .-----------------------------------------------------------.
* track: | K.....K.........K........K.......K.......K...........K... |
* '-----------------------------------------------------------'
* 0 1 2 3 4
* .------------^ ^ .----------^ ^
* / .-------------' / .------------------'
* / / .-----' /
* .--------------. .--------------.
* | segment 1 | | segment 2 |
* '--------------' '--------------'
*
* The challenge here is to cut out the right pieces of the track for each of
* the playback segments. This fortunatly can easily be done with the SEGMENT
* events of gstreamer.
*
* For playback of segment 1, we need to provide the decoder with the keyframe
* (a), in the above figure, but we must instruct it only to output the decoded
* data between second 1 and 2. We do this with a SEGMENT event for 1 to 2, time
* position set to the time of the segment: 0.
*
* We then proceed to push data from keyframe (a) to frame (b). The decoder
* decodes but clips all before media_time 1.
*
* After finishing a segment, we push out a new SEGMENT event with the clipping
* boundaries of the new data.
*
* This is a good usecase for the GStreamer accumulated SEGMENT events.
*/
struct _QtDemuxSegment
{
/* global time and duration, all gst time */
@ -1270,7 +1328,19 @@ gst_qtdemux_activate_segment (GstQTDemux * qtdemux, QtDemuxStream * stream,
return FALSE;
}
stop = segment->media_stop;
/* qtdemux->segment.stop is in outside-time-realm, whereas
* segment->media_stop is in track-time-realm.
*
* In order to compare the two, we need to bring segment.stop
* into the track-time-realm */
if (qtdemux->segment.stop == -1)
stop = segment->media_stop;
else
stop =
MIN (segment->media_stop,
qtdemux->segment.stop - segment->time + segment->media_start);
if (qtdemux->segment.rate >= 0) {
start = MIN (segment->media_start + seg_time, stop);
time = offset;