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qtdemux: Provide a 2 frames lead-in for audio decoders

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AAC and various other audio codecs need a couple frames of lead-in to
decode it properly. The parser elements like aacparse take care of it
via gst_base_parse_set_frame_rate, but when inside a container, the
demuxer is doing the seek segment handling and never gives lead-in
data downstream.
Handle this similar to going back to a keyframe with video, in the
same place. Without a lead-in, the start of the segment is silence,
when it shouldn't, which becomes especially evident in NLE use cases.
This commit is contained in:
Mart Raudsepp 2019-06-05 23:13:33 +03:00
parent 9b348e755c
commit cbfa4531ee
1 changed files with 15 additions and 2 deletions
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17
gst/isomp4/qtdemux.c
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@ -5148,6 +5148,19 @@ gst_qtdemux_activate_segment (GstQTDemux * qtdemux, QtDemuxStream * stream,
/* find keyframe of the target index */
kf_index = gst_qtdemux_find_keyframe (qtdemux, stream, index, FALSE);
/* go back two frames to provide lead-in for non-raw audio decoders */
if (stream->subtype == FOURCC_soun && !stream->need_clip) {
guint32 old_index = kf_index;
kf_index = MAX (kf_index, 2) - 2;
if (qtdemux_parse_samples (qtdemux, stream, kf_index)) {
GST_DEBUG_OBJECT (stream->pad,
"Moving backwards %u frames to ensure sufficient sound lead-in",
old_index - kf_index);
} else {
kf_index = old_index;
}
}
/* if we move forwards, we don't have to go back to the previous
* keyframe since we already sent that. We can also just jump to
* the keyframe right before the target index if there is one. */
@ -5171,9 +5184,9 @@ gst_qtdemux_activate_segment (GstQTDemux * qtdemux, QtDemuxStream * stream,
}
} else {
GST_DEBUG_OBJECT (stream->pad,
"moving backwards to keyframe at %u "
"moving backwards to %sframe at %u "
"(pts %" GST_TIME_FORMAT " dts %" GST_TIME_FORMAT " )",
kf_index,
(stream->subtype == FOURCC_soun) ? "audio " : "key", kf_index,
GST_TIME_ARGS (QTSAMPLE_PTS (stream, &stream->samples[kf_index])),
GST_TIME_ARGS (QTSAMPLE_DTS (stream, &stream->samples[kf_index])));
gst_qtdemux_move_stream (qtdemux, stream, kf_index);