[patch][RFC] mpeg-ts not packetized properly over UDP

[aviad rozenhek]

when using ffmpeg to mux an mpegts stream over UDP, the data is not
packetized properly.
the default packet size of UDP is 1472, which is not an integer multiple of
188 (the TS packet size).
this causes problems if UDP packets are dropped or reordered.

this can be worked around from the commandline if changing cmdline from:
*> ffmpeg -re -i <input_file> -f mpegts udp://localhost:1234*
to:
*> ffmpeg -re -i <input_file> -f mpegts udp://localhost:1234?pkt_size=188*
*
*
however I think this makes it difficult for user to use properly.
attached is a simple (but not as efficient as possible) patch that fixes
this problem, by flushing after writing every TS packet.

[aviad rozenhek]

Post by aviad rozenhek
when using ffmpeg to mux an mpegts stream over UDP, the data is not
packetized properly.
the default packet size of UDP is 1472, which is not an integer multiple of
188 (the TS packet size).
this causes problems if UDP packets are dropped or reordered.
*> ffmpeg -re -i <input_file> -f mpegts udp://localhost:1234*
*> ffmpeg -re -i <input_file> -f mpegts udp://localhost:1234?pkt_size=188
*
*
*
however I think this makes it difficult for user to use properly.
attached is a simple (but not as efficient as possible) patch that fixes
this problem, by flushing after writing every TS packet.

ping?

[Michael Niedermayer]

Post by aviad rozenhek
when using ffmpeg to mux an mpegts stream over UDP, the data is not
packetized properly.
the default packet size of UDP is 1472, which is not an integer multiple of
188 (the TS packet size).
this causes problems if UDP packets are dropped or reordered.
*> ffmpeg -re -i <input_file> -f mpegts udp://localhost:1234*
*> ffmpeg -re -i <input_file> -f mpegts udp://localhost:1234?pkt_size=188*
*
*
however I think this makes it difficult for user to use properly.
attached is a simple (but not as efficient as possible) patch that fixes
this problem, by flushing after writing every TS packet.

the udp packet size should be a multiple of the underlaying streams packet
size when possible and it should be as large as possible
making it 188 is not ok, this has too much overhead

[...]

[Måns Rullgård]

Post by Michael Niedermayer

Post by aviad rozenhek
when using ffmpeg to mux an mpegts stream over UDP, the data is not
packetized properly.
the default packet size of UDP is 1472, which is not an integer multiple of
188 (the TS packet size).
this causes problems if UDP packets are dropped or reordered.
*> ffmpeg -re -i <input_file> -f mpegts udp://localhost:1234*
*> ffmpeg -re -i <input_file> -f mpegts udp://localhost:1234?pkt_size=188*
*
*
however I think this makes it difficult for user to use properly.
attached is a simple (but not as efficient as possible) patch that fixes
this problem, by flushing after writing every TS packet.

the udp packet size should be a multiple of the underlaying streams packet
size when possible and it should be as large as possible
making it 188 is not ok, this has too much overhead

It is common to send 7 188-byte TS packets per UDP packet as this is
the maximum number which fits in a 1500-byte MTU.

[Stefan de Konink]

Post by Måns Rullgård
It is common to send 7 188-byte TS packets per UDP packet as this is
the maximum number which fits in a 1500-byte MTU.

Doing an actual check what MTU the of the outgoing network is, and base
the value on that? Although the 7*188 probably covers all 'usual'
configurations (including VLAN trunking etc.)


Stefan

[aviad rozenhek]

Post by Michael Niedermayer

Post by aviad rozenhek
when using ffmpeg to mux an mpegts stream over UDP, the data is not
packetized properly.
the default packet size of UDP is 1472, which is not an integer multiple

of

Post by aviad rozenhek
188 (the TS packet size).
this causes problems if UDP packets are dropped or reordered.

the udp packet size should be a multiple of the underlaying streams packet
size when possible and it should be as large as possible
making it 188 is not ok, this has too much overhead

how about a solution in the spirit of this new attached patch?

[aviad rozenhek]

Post by aviad rozenhek

Post by Michael Niedermayer

Post by aviad rozenhek
when using ffmpeg to mux an mpegts stream over UDP, the data is not
packetized properly.
the default packet size of UDP is 1472, which is not an integer multiple

of

Post by aviad rozenhek
188 (the TS packet size).
this causes problems if UDP packets are dropped or reordered.

the udp packet size should be a multiple of the underlaying streams packet
size when possible and it should be as large as possible
making it 188 is not ok, this has too much overhead

how about a solution in the spirit of this new attached patch?

ping

[Carl Eugen Hoyos]

Post by aviad rozenhek
how about a solution in the spirit of this new attached patch?

Your patch contains a cosmetic change (that is forbidden) that adds a tab (which
is also forbidden), please consider using tools/patcheck.

Carl Eugen

[aviad rozenhek]

Post by Carl Eugen Hoyos

Post by aviad rozenhek
how about a solution in the spirit of this new attached patch?

Your patch contains a cosmetic change (that is forbidden) that adds a tab (which
is also forbidden), please consider using tools/patcheck.
Carl Eugen

sorry about that.
I can submit a proper patch if the idea behind it is agreed on.

[aviad rozenhek]

Post by Carl Eugen Hoyos

Post by aviad rozenhek
how about a solution in the spirit of this new attached patch?

Your patch contains a cosmetic change (that is forbidden) that adds a tab (which
is also forbidden), please consider using tools/patcheck.
Carl Eugen

sorry about that, here an updated patch.
it doesn't change anything for protocols that have no packet sizes such as
files, and changes the buffer for protocols that do.
for udp the buffer changes to 1316 bytes.

[Carl Eugen Hoyos]

+ init_put_byte(s->pb, s->pb->buffer, max_packet_size,
+ s->pb->write_flag, s->pb->opaque, s->pb->read_packet,
+ s->pb->write_packet, s->pb->seek);
+ init_put_byte(s->pb, s->pb->buffer, max_packet_size,
+ s->pb->write_flag, s->pb->opaque, s->pb->read_packet,

Carl Eugen

[aviad rozenhek]

+ init_put_byte(s->pb, s->pb->buffer, max_packet_size,
+ s->pb->write_flag, s->pb->opaque, s->pb->read_packet,
+ s->pb->write_packet, s->pb->seek);
+ init_put_byte(s->pb, s->pb->buffer, max_packet_size,
+ s->pb->write_flag, s->pb->opaque,

s->pb->read_packet,
Carl Eugen

fixed

[Carl Eugen Hoyos]

+ init_put_byte(s->pb, s->pb->buffer, max_packet_size,
+ s->pb->write_flag, s->pb->opaque,

s->pb->read_packet,
Carl Eugen

fixed
+ av_log(s, AV_LOG_ERROR, "max packet size %d", max_packet_size);

This line looks suspicious (as if it is printed in any case with a rather high
log level).

Carl Eugen

[aviad rozenhek]

Post by Carl Eugen Hoyos

+ init_put_byte(s->pb, s->pb->buffer, max_packet_size,
+ s->pb->write_flag, s->pb->opaque,

s->pb->read_packet,
Carl Eugen

fixed
+ av_log(s, AV_LOG_ERROR, "max packet size %d", max_packet_size);

This line looks suspicious (as if it is printed in any case with a rather high
log level).
Carl Eugen

Your absolutely right, its just a debugging line
shame on me for hacking at hours way past my bedtime.
fixed

[atv_ffmpeg]

Just modify udp.c in the folder called libavformat, change 1472 to 1316,
function 'udp_open'. It works fine. I already did it.

Post by aviad rozenhek
when using ffmpeg to mux an mpegts stream over UDP, the data is not
packetized properly.
the default packet size of UDP is 1472, which is not an integer multiple of
188 (the TS packet size).
this causes problems if UDP packets are dropped or reordered.
*> ffmpeg -re -i <input_file> -f mpegts udp://localhost:1234*
*> ffmpeg -re -i <input_file> -f mpegts udp://localhost:1234?pkt_size=188*
*
*
however I think this makes it difficult for user to use properly.
attached is a simple (but not as efficient as possible) patch that fixes
this problem, by flushing after writing every TS packet.
--
Aviad Rozenhek
_______________________________________________
ffmpeg-devel mailing list
https://lists.mplayerhq.hu/mailman/listinfo/ffmpeg-devel

[Alexandre Ferrieux]

Post by atv_ffmpeg
Just modify udp.c in the folder called libavformat, change 1472 to 1316,
function 'udp_open'. It works fine. I already did it.

1) Don't top post.

2) Of course it works. But hard-coding the TS-specific magic number 7*188 in place of the generic, MTU-related 1472 in
the muxer+codec-agnostic module udp.c, while a command-line override does it, is a bad idea.

Maybe some kind of information could flow from the TS container to the UDP url handler, to set it automatically ? Not
familiar enough with that part though. The command-line override is perfect in the meanime.

-Alex

Post by atv_ffmpeg

Post by aviad rozenhek
when using ffmpeg to mux an mpegts stream over UDP, the data is not
packetized properly.
the default packet size of UDP is 1472, which is not an integer multiple of
188 (the TS packet size).
this causes problems if UDP packets are dropped or reordered.
*> ffmpeg -re -i<input_file> -f mpegts udp://localhost:1234*
*> ffmpeg -re -i<input_file> -f mpegts udp://localhost:1234?pkt_size=188*
*
*
however I think this makes it difficult for user to use properly.
attached is a simple (but not as efficient as possible) patch that fixes
this problem, by flushing after writing every TS packet.
--
Aviad Rozenhek
_______________________________________________
ffmpeg-devel mailing list
https://lists.mplayerhq.hu/mailman/listinfo/ffmpeg-devel

_______________________________________________
ffmpeg-devel mailing list
https://lists.mplayerhq.hu/mailman/listinfo/ffmpeg-devel

[Carl Eugen Hoyos]

Post by Alexandre Ferrieux
1) Don't top post.

And please cut your quotes and please fix your line length.

Carl Eugen