On Sun, 4 Aug 2019, Andreas Håkon wrote:
Hi Marton,
‐‐‐‐‐‐‐ Original Message ‐‐‐‐‐‐‐
v2: a video is stream is preferred if there are no programs, just like before
the patch.
Thank you for your effort!
However, something is wrong with this patch regarding PCR intervals.
First, try this example (using the file shared by Michael
https://trac.ffmpeg.org/raw-attachment/ticket/3714/FFmpeg%20Sample_cut.ts ):
% ffmpeg -loglevel info -y -i Sample_cut.ts \
-map '0:v:0' -c:v:0 copy \
-map '0:v:0' -c:v:1 copy \
-map '0:a:0' -c:a:0 copy \
-pat_period 1 \
-program st=0,1,2 \
-program st=0,2 \
-program st=1,2 \
-program st=3 \
-sdt_period 1 \
this_was_less_than_2560000-marton.ts
This command line does not seem correct, there is no stream 3, also in
order to specify multiple streams per program you have to use this syntax:
-program st=0:st=2.
Then you get:
[mpegts @ 0x3046880] service 1 using PCR in pid=256
[mpegts @ 0x3046880] service 2 using PCR in pid=256
[mpegts @ 0x3046880] service 3 using PCR in pid=257
[mpegts @ 0x3046880] service 4 using PCR in pid=258
Until here all seems correct.
However, if you analyze the PCR intervals:
- 256: PCR_count: 0x3 (3) => repetition rate: 0,299 seconds
- 257: PCR_count: 0x3 (3) => repetition rate: 0,305 seconds
- 258: PCR_count: 0x4 (4) => repetition rate: 0,139 seconds
(You can check it with the DVB Inspector tool or any other)
And regular repetition rate are 0,450 seconds (with ffmpeg).
450m PCR seems wrong. ISO/IEC13818-1 specifies
an interval of 100 ms, while DVB recommends 40 ms PCR-s.
What was the PCR interval before the patch? 450 ms seems like the
keyframe interval of your video, because for keyframes you always get
a PCR with the current code.
Keep in mind that according to this
https://ffmpeg.org/pipermail/ffmpeg-devel/2016-March/192040.html
PCR in VBR streams never worked correctly.
CBR with multiple programs was also problematic, because instead of
counting all packets the counter only counted the packets of a service.
The way I see it PCR generation needs a serious rework, I will post a
patch for that, you will have to apply it on top of this series.
So...
@@ -57,8 +57,6 @@ typedef struct MpegTSService {
uint8_t name[256];
uint8_t provider_name[256];
int pcr_pid;
- int pcr_packet_count;
- int pcr_packet_period;
AVProgram *program;
} MpegTSService;
Why you remove the "pcr_packet_period" from services?
I know that the value can be the same for all services inside the
same TS, but the PCR interval is per service, and not per TS.
It is per PID now instead of per service.
@@ -1015,8 +1032,7 @@ static int mpegts_init(AVFormatContext *s)
else
av_log(s, AV_LOG_VERBOSE, "muxrate %d, ", ts->mux_rate);
av_log(s, AV_LOG_VERBOSE,
- "pcr every %d pkts, sdt every %d, pat/pmt every %d pkts\\n",
- service->pcr_packet_period,
+ "sdt every %d, pat/pmt every %d pkts\\n",
ts->sdt_packet_period, ts->pat_packet_period);
The information about the PCR interval is a must have. Please, don't remove it!
It is written out in select_pcr_streams.
@@ -1198,12 +1214,12 @@ static void mpegts_write_pes(AVFormatContext *s,
AVStream *st,
force_pat = 0;
write_pcr = 0;
- if (ts_st->pid == ts_st->service->pcr_pid) {
+ if (ts_st->pcr_packet_period) {
if (ts->mux_rate > 1 || is_start) // VBR pcr period is based on
frames
- ts_st->service->pcr_packet_count++;
- if (ts_st->service->pcr_packet_count >=
- ts_st->service->pcr_packet_period) {
- ts_st->service->pcr_packet_count = 0;
+ ts_st->pcr_packet_count++;
+ if (ts_st->pcr_packet_count >=
+ ts_st->pcr_packet_period) {
+ ts_st->pcr_packet_count = 0;
}
}
In this way, with multiple services (the reason for this patch) you're
generating a
Transport Stream with PCR streams sharing the interval period. That's a new
serious BUG!
No, ts_st is different for each stream (each PID).
For each service it's one PCR. And the interval of each PCR for one stream is
computed from the last PCR of the same stream. It can't be calculated from the
last
PCR of any other stream.
ts_st is different for each stream, it is not common.
Please, fix this bug before merging this patch.
@@ -1236,7 +1252,7 @@ static void mpegts_write_pes(AVFormatContext *s, AVStream
*st,
}
if (key && is_start && pts != AV_NOPTS_VALUE) {
// set Random Access for key frames
- if (ts_st->pid == ts_st->service->pcr_pid)
+ if (ts_st->pcr_packet_period)
write_pcr = 1;
set_af_flag(buf, 0x40);
q = get_ts_payload_start(buf);
Just the same problem.
Regards,
Marton
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