Hi,
Patch to generate aligned Teletext PES packets using the MPEG-TS muxer
when the TS header contains data.
Regards.
A.H.
---
From 5b476153e0fcced53afa1b77543c2e386f08c504 Mon Sep 17 00:00:00 2001
From: Andreas Hakon <andreas.ha...@protonmail.com>
Date: Wed, 22 May 2019 15:36:50 +0100
Subject: [PATCH] libavformat/mpegtsenc: adaptive alignment for teletext PES
packets
The code that generates the PES packets for Teletext data aligns the PES packets
with the boundaries of the TS packets. The strategy used is to insert padding
stuff into the PES header. The size of this padding alignment currently has a
fixed size of 36 bytes. And this value is correct when all of the Teletext
TS packets have payload only. However, inserting some data into the TS header
breaks this assumption. In this case, the Teletext PES packets are not aligned
and the end of the PES packet is inserted into an additional TS packet with a
large amount of TS padding.
This patch calculates the size of the TS header in order to reduce the size of
the PES padding and thus accommodate the PES packet to the TS boundaries.
In this way no additional TS packets are produced.
Signed-off-by: Andreas Hakon <andreas.ha...@protonmail.com>
libavformat/mpegtsenc.c | 7 +++++--
1 file changed, 5 insertions(+), 2 deletions(-)
diff --git a/libavformat/mpegtsenc.c b/libavformat/mpegtsenc.c
index fc0ea22..f1772ac 100644
--- a/libavformat/mpegtsenc.c
+++ b/libavformat/mpegtsenc.c
@@ -1328,8 +1328,11 @@ static void mpegts_write_pes(AVFormatContext *s,
AVStream *st,
header_len += 3;
}
if (is_dvb_teletext) {
- pes_header_stuffing_bytes = 0x24 - header_len;
- header_len = 0x24;
+ int header_stuff = (get_ts_payload_start(buf) - buf) - 4;
+ if (header_stuff - header_len > 0x24)
+ header_stuff = 0;
+ pes_header_stuffing_bytes = 0x24 - header_len - header_stuff;
+ header_len = 0x24 - header_stuff;
}
len = payload_size + header_len + 3;
/* 3 extra bytes should be added to DVB subtitle payload: 0x20
0x00 at the beginning and trailing 0xff */
--
1.7.10.4
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