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[FFmpeg-devel] libavformat/mpegtsenc: enforce PCR packets without payload

Message ID T70zVfbb3ne8BhER4Szps9Sk27Lmgp6LkBqDZJLbrL3gfwQJVomamUYPG2KnOCnHn6UKqofQix5JSJ4965iHl75m41WeHHNNu0oKkJosZXg=@protonmail.com
State New
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Commit Message

Andreas Håkon April 25, 2019, 9:07 a.m. UTC 
Hi,

A patch for a new optional parameter for the mpegtsenc muxer.

Regards.
A.H.

---
From 7f9f1a992615e15121b661d4cd1b9c1e32e1c894 Mon Sep 17 00:00:00 2001
From: Andreas Hakon <andreas.hakon@protonmail.com>
Date: Thu, 25 Apr 2019 09:49:29 +0100
Subject: [PATCH] libavformat/mpegtsenc: enforce PCR packets without payload

This patch provides a new optional parameter for the mpegtsenc muxer.
The parameter "-pcr_without_payload" can be used to override the default
behaviour of writing PCR timestamps in TS packets with payload.
Using a value greater than 0 all TS packets carrying PCR timestamps will
be forced to have an empty payload. Otherwise (with 0) the regular behaviour is
used and PCR packets can have payload. Futhermore with a value greater than 1
the packet with the PCR will be repeated the number of times indicated.
The default value is "-pcr_without_payload 0", which corresponds to the current
behaviour.
This can be handy for many reasons.

Signed-off-by: Andreas Hakon <andreas.hakon@protonmail.com>
---
 doc/muxers.texi         |    5 +++++
 libavformat/mpegtsenc.c |   18 ++++++++++++++----
 2 files changed, 19 insertions(+), 4 deletions(-)

Comments

Ali KIZIL April 25, 2019, 2:23 p.m. UTC | #1 
Andreas Håkon <andreas.hakon@protonmail.com>, 25 Nis 2019 Per, 12:07
tarihinde şunu yazdı:

> Hi,
>
> A patch for a new optional parameter for the mpegtsenc muxer.
>
> Regards.
> A.H.
>
> ---_______________________________________________
>

Is this patch related with "[FFmpeg-devel] [PATCH] libavformat: forced PCR
pid in mpegts muxer" patchwork ?

Is the purpose of the patch to avoid null stuffing in forced pcr pid ?

I can not figure out the usage. A texi can be useful.
Normally, if PCR in on Video PID, why should I prefer to avoid video
payload ?
Andreas Håkon April 25, 2019, 2:49 p.m. UTC | #2 
‐‐‐‐‐‐‐ Original Message ‐‐‐‐‐‐‐
On Thursday, 25 de April de 2019 16:23, Ali KIZIL <alikizil@gmail.com> wrote:

> Andreas Håkon andreas.hakon@protonmail.com, 25 Nis 2019 Per, 12:07
> tarihinde şunu yazdı:
>
> > Hi,
> > A patch for a new optional parameter for the mpegtsenc muxer.
> > Regards.
> > A.H.
> > ---_______________________________________________
>
> Is this patch related with "[FFmpeg-devel] [PATCH] libavformat: forced PCR
> pid in mpegts muxer" patchwork ?

No. They're complementary, but totally different patches/objectives!

>
> Is the purpose of the patch to avoid null stuffing in forced pcr pid ?

No. The purpose is to avoid having PCR marks in packets with payload.

>
> I can not figure out the usage. A texi can be useful.
> Normally, if PCR in on Video PID, why should I prefer to avoid video
> payload ?
>

When you move the PCR marks to empty packets then you can transform the
Transport Stream without touching the PES packets at all. Imagine a TS
processor that duplicates or process the PCR packets for other purposes.
As these packets doesn't have any payload the stream processor is free
to do it whatever it needs. This is just one example. This option can
be useful in various scenarios. In my research the target are several
multi-resolution streams for mobile devices.

In any case I have to say that this patch is completely transparent
and only adds optional functionality.

Regards.
A.H.

---
Ali KIZIL April 25, 2019, 3:36 p.m. UTC | #3 
Andreas Håkon <andreas.hakon@protonmail.com>, 25 Nis 2019 Per, 17:49
tarihinde şunu yazdı:

>
>
>
> ‐‐‐‐‐‐‐ Original Message ‐‐‐‐‐‐‐
> On Thursday, 25 de April de 2019 16:23, Ali KIZIL <alikizil@gmail.com>
> wrote:
>
> > Andreas Håkon andreas.hakon@protonmail.com, 25 Nis 2019 Per, 12:07
> > tarihinde şunu yazdı:
> >
> > > Hi,
> > > A patch for a new optional parameter for the mpegtsenc muxer.
> > > Regards.
> > > A.H.
> > > ---_______________________________________________
> >
> > Is this patch related with "[FFmpeg-devel] [PATCH] libavformat: forced
> PCR
> > pid in mpegts muxer" patchwork ?
>
> No. They're complementary, but totally different patches/objectives!
>
> >
> > Is the purpose of the patch to avoid null stuffing in forced pcr pid ?
>
> No. The purpose is to avoid having PCR marks in packets with payload.
>
> >
> > I can not figure out the usage. A texi can be useful.
> > Normally, if PCR in on Video PID, why should I prefer to avoid video
> > payload ?
> >
>
> When you move the PCR marks to empty packets then you can transform the
> Transport Stream without touching the PES packets at all. Imagine a TS
> processor that duplicates or process the PCR packets for other purposes.
> As these packets doesn't have any payload the stream processor is free
> to do it whatever it needs. This is just one example. This option can
> be useful in various scenarios. In my research the target are several
> multi-resolution streams for mobile devices.
>
> In any case I have to say that this patch is completely transparent
> and only adds optional functionality.
>
> Regards.
> A.H.
>
> ---
>

I got the point. Yet, sorry for being curious, would can affect TR101 290
analyze results  and/or null stuffing on CBR mpegts out?
I can do these tests if needed, by tomorrow.
Andreas Håkon April 25, 2019, 4:27 p.m. UTC | #4 
‐‐‐‐‐‐‐ Original Message ‐‐‐‐‐‐‐
On Thursday, 25 de April de 2019 17:36, Ali KIZIL <alikizil@gmail.com> wrote:

> Andreas Håkon andreas.hakon@protonmail.com, 25 Nis 2019 Per, 17:49
> tarihinde şunu yazdı:
>
> I got the point. Yet, sorry for being curious, would can affect TR101 290
> analyze results and/or null stuffing on CBR mpegts out?
> I can do these tests if needed, by tomorrow.
>

Don't worry! I'm glad to discuss it.

And no, it doesn't violate the rules of the standards in any way.
So pass all the analyzers. And it never generates null stuffing (pid 8191).

It even correctly agrees with the restriction of not increasing the CC
counter when no payload is found in the TS packet.

So please check it with as many analyzers as you can.
I'm sure it'll pass them.

Regards,
A.H.

---
Andreas Håkon April 29, 2019, 7:06 a.m. UTC | #5 
‐‐‐‐‐‐‐ Original Message ‐‐‐‐‐‐‐
On Thursday, 25 de April de 2019 11:07, Andreas Håkon <andreas.hakon@protonmail.com> wrote:

> Hi,
>
> A patch for a new optional parameter for the mpegtsenc muxer.
>
> Regards.
> A.H.
>


Hi Ali KIZIL,

You do the validation tests?



Hi Michael Niedermayer,

Have you been able to review this new functionality?
It is very useful and has no side effects.


Regards.
A.H.


---
diff mbox

Patch

diff --git a/doc/muxers.texi b/doc/muxers.texi
index 83ae017..9acdee3 100644
--- a/doc/muxers.texi
+++ b/doc/muxers.texi
@@ -1564,6 +1564,11 @@  Set a constant muxrate. Default is VBR.
 @item pes_payload_size @var{integer}
 Set minimum PES packet payload in bytes. Default is @code{2930}.
 
+@item pcr_without_payload @var{integer}
+Generates PCR packets without payload. When the value is greater than 1
+it repeats the PCR packet N times. With a 0 value it generates regular
+PCR packets with payload. Default is @code{0}.
+
 @item mpegts_flags @var{flags}
 Set mpegts flags. Accepts the following options:
 @table @samp
diff --git a/libavformat/mpegtsenc.c b/libavformat/mpegtsenc.c
index fc0ea22..0cc42cd 100644
--- a/libavformat/mpegtsenc.c
+++ b/libavformat/mpegtsenc.c
@@ -97,6 +97,7 @@  typedef struct MpegTSWrite {
     int pmt_start_pid;
     int start_pid;
     int m2ts_mode;
+    int pcr_repetition;
 
     int reemit_pat_pmt; // backward compatibility
 
@@ -1093,12 +1094,13 @@  static void mpegts_insert_null_packet(AVFormatContext *s)
 }
 
 /* Write a single transport stream packet with a PCR and no payload */
-static void mpegts_insert_pcr_only(AVFormatContext *s, AVStream *st)
+static void mpegts_insert_pcr_only(AVFormatContext *s, AVStream *st, int repetition)
 {
     MpegTSWrite *ts = s->priv_data;
     MpegTSWriteStream *ts_st = st->priv_data;
     uint8_t *q;
     uint8_t buf[TS_PACKET_SIZE];
+    int i;
 
     q    = buf;
     *q++ = 0x47;
@@ -1119,7 +1121,9 @@  static void mpegts_insert_pcr_only(AVFormatContext *s, AVStream *st)
     /* stuffing bytes */
     memset(q, 0xFF, TS_PACKET_SIZE - (q - buf));
     mpegts_prefix_m2ts_header(s);
-    avio_write(s->pb, buf, TS_PACKET_SIZE);
+    for (i=0; i<repetition; i++) {
+        avio_write(s->pb, buf, TS_PACKET_SIZE);
+    }
 }
 
 static void write_pts(uint8_t *q, int fourbits, int64_t pts)
@@ -1212,12 +1216,15 @@  static void mpegts_write_pes(AVFormatContext *s, AVStream *st,
             (dts - get_pcr(ts, s->pb) / 300) > delay) {
             /* pcr insert gets priority over null packet insert */
             if (write_pcr)
-                mpegts_insert_pcr_only(s, st);
+                mpegts_insert_pcr_only(s, st, ts->pcr_repetition < 1 ? 1 : ts->pcr_repetition);
             else
                 mpegts_insert_null_packet(s);
             /* recalculate write_pcr and possibly retransmit si_info */
             continue;
         }
+        if (write_pcr && ts->pcr_repetition > 0) {
+            mpegts_insert_pcr_only(s, st, ts->pcr_repetition);
+        }
 
         /* prepare packet header */
         q    = buf;
@@ -1241,7 +1248,7 @@  static void mpegts_write_pes(AVFormatContext *s, AVStream *st,
             set_af_flag(buf, 0x40);
             q = get_ts_payload_start(buf);
         }
-        if (write_pcr) {
+        if (write_pcr && ts->pcr_repetition == 0) {
             set_af_flag(buf, 0x10);
             q = get_ts_payload_start(buf);
             // add 11, pcr references the last byte of program clock reference base
@@ -1926,6 +1933,9 @@  static const AVOption options[] = {
     { "pes_payload_size", "Minimum PES packet payload in bytes",
       offsetof(MpegTSWrite, pes_payload_size), AV_OPT_TYPE_INT,
       { .i64 = DEFAULT_PES_PAYLOAD_SIZE }, 0, INT_MAX, AV_OPT_FLAG_ENCODING_PARAM },
+    { "pcr_without_payload", "Generate PCR packets without payload",
+      offsetof(MpegTSWrite, pcr_repetition), AV_OPT_TYPE_INT,
+      { .i64 = 0 }, 0, INT_MAX, AV_OPT_FLAG_ENCODING_PARAM },
     { "mpegts_flags", "MPEG-TS muxing flags",
       offsetof(MpegTSWrite, flags), AV_OPT_TYPE_FLAGS, { .i64 = 0 }, 0, INT_MAX,
       AV_OPT_FLAG_ENCODING_PARAM, "mpegts_flags" },