This patch fixes strange seeking behavior i have observed in mpv when using the
libopenmpt demuxer, caused by mismatch in position state between the demuxer
and underlying libopenmpt library. Not setting the presentation timestamp
field of the AVPacket caused it to be guessed by libavformat, but the guess
didn't take seeking into account, so after seeking libopenmpt produced packets
at the new seeked position but they were then presented as if they belong to
the old position! A quick check for this behavior is to open a tracker tracker
module that is, for example 2 minutes and a few seconds long in mpv, and then
press "up" 2 times (which would seek 2 minutes forward): buggy demuxer causes
mpv to exit immediately after seek because of an EOF, with non-buggy demuxer
mpv will play the last few seconds of the song and then exit.
I found the bug when writing my own demuxer for an obscure audio format (which
i'm not quite sure if i should submit too) as i was using the libopenmpt one as
a reference and copied the bug too. Testing was done on 6.1.1, but libopenmpt
demuxer's code didn't really change since then so it should be relevant for the
latest one too (unless the default value for pkt->pts changed to take seeking
into account), and either way it makes more sense to expose information that is
very much available to the demuxer rather than leave it to be guessed.
From 451691febac466cee37d9b836228e30c53813d60 Mon Sep 17 00:00:00 2001
From: Kimapr <kimapr...@gmail.com>
Date: Mon, 28 Jul 2025 06:32:27 +0500
Subject: [PATCH] libopenmpt: fix seeking
---
libavformat/libopenmpt.c | 3 +++
1 file changed, 3 insertions(+)
diff --git a/libavformat/libopenmpt.c b/libavformat/libopenmpt.c
index c270a60cb2..d383d65ad8 100644
--- a/libavformat/libopenmpt.c
+++ b/libavformat/libopenmpt.c
@@ -171,6 +171,8 @@ static int read_packet_openmpt(AVFormatContext *s, AVPacket *pkt)
if ((ret = av_new_packet(pkt, AUDIO_PKT_SIZE)) < 0)
return ret;
+ double pos = openmpt_module_get_position_seconds(openmpt->module);
+
switch (openmpt->ch_layout.nb_channels) {
case 1:
ret = openmpt_module_read_float_mono(openmpt->module, openmpt->sample_rate,
@@ -195,6 +197,7 @@ static int read_packet_openmpt(AVFormatContext *s, AVPacket *pkt)
}
pkt->size = ret * (openmpt->ch_layout.nb_channels * 4);
+ pkt->pts = llrint(pos * AV_TIME_BASE);
return 0;
}
--
2.49.0
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