Negative Presentation Timestamp of RTSP

Answered

DW R&D

December 12, 2018 08:31

I get a video stream with ffmpeg rtsp.
The presentation time of AVPacket is expressed as positive and suddenly it changes to negative.
There are quite a number of such sections.
Because of this, I can not get the recording timeline information.
Is this a bug or normal?
How do I get the correct presentation time?

ex) rtsp://demo:demo@100.32.247.140:7001/proxy/rtsp/ae310607-6bd9-931e-ba28-689bd8da3048/d7151446-cfee-8a0f-2155-41b7627ff0ac?stream=0&pos=1544547653322

code)

AVPacket packet;

AVFormatContext *pAvFmtCtx;

NSLog(@"=>dts: %lld, pts:%lld, duration:%lld, num:%d, den:%d, sec:%lld", packet->dts, packet->pts, packet->duration, pAvFmtCtx->streams[stream]->time_base.num, pAvFmtCtx->streams[stream]->time_base.den, sec/1000);

-----------------------------------------------------------------------------------------

=>dts: 295380, pts:295380, duration:12857, num:1, den:90000, sec:109

=>dts: 306090, pts:306090, duration:12857, num:1, den:90000, sec:113

=>dts: 291240, pts:291240, duration:6480, num:1, den:90000, sec:105

=>dts: 297720, pts:297720, duration:6480, num:1, den:90000, sec:108

=>dts: 318150, pts:318150, duration:12857, num:1, den:90000, sec:117

=>dts: -383130, pts:-383130, duration:6480, num:1, den:90000, sec:-133

=>dts: -376650, pts:-376650, duration:6480, num:1, den:90000, sec:-131

=>dts: 332910, pts:332910, duration:12857, num:1, den:90000, sec:122

=>dts: -376650, pts:-376650, duration:6480, num:1, den:90000, sec:-131

=>dts: -370170, pts:-370170, duration:6480, num:1, den:90000, sec:-129

=>dts: -367290, pts:-367290, duration:6480, num:1, den:90000, sec:-128

Thank you.

Comments

7 comments

Permanently deleted user

December 12, 2018 14:42
Dear Paul,

Thanks a lot for your report, it seems to be an issue worth investigating on our side. We are already working on it, I will come back to you as soon as we have any news.

Thank you again, hopefully we will have some news for you soon.
0
Tony Luce

January 02, 2019 19:14
Hey Maxim - any updates here?
0
Permanently deleted user

January 09, 2019 10:14 Edited
Hi Tony, Paul,

Sorry for late reply, we had a holiday season here. I just checked the status of the task, it is still in progress, no news so far, sorry.

I will try to push it a bit.
0
Permanently deleted user

March 14, 2019 13:23 Edited
Hi Pual,

Is issue still reproducible?
0
DW R&D

March 15, 2019 17:28 Edited
The server still has the problem.
You can see the negative pts when you connect to the site below.

server: v3.2.0.28341

rtsp://demo:demo@100.32.247.140:7001/{bc5a13a1-5823-711a-c675-7176604eee7e}?stream=0&pos=1551120562000
0

Permanently deleted user

March 15, 2019 17:56 Edited

What tool do you use? The issue in first frames only or many times in random places?

ffprobe print such result: 

ffprobe  -show_frames -show_entries frame=pkt_dts_time  "rtsp://demo:demo@100.32.247.140:7001/{bc5a13a1-5823-711a-c675-7176604eee7e}?stream=0&pos=1551120562000" 
ffprobe version n3.1.9 Copyright (c) 2007-2017 the FFmpeg developers 
 built with gcc 5.4.0 (Ubuntu 5.4.0-6ubuntu1~16.04.10) 20160609 
 libavutil      55. 28.100 / 55. 78.100 
 libavcodec     57. 48.101 / 57.107.100 
 libavformat    57. 41.100 / 57. 83.100 
 libavdevice    57.  0.101 / 57. 10.100 
 libavfilter     6. 47.100 /  6.107.100 
 libswscale      4.  1.100 /  4.  8.100 
 libswresample   2.  1.100 /  2.  9.100 
 libpostproc    54.  0.100 / 54.  7.100 
[rtsp @ 0x17a61e0] CSeq 1 expected, 0 received. 
Input #0, rtsp, from 'rtsp://demo:demo@100.32.247.140:7001/{bc5a13a1-5823-711a-c675-7176604eee7e}?stream=0&pos=1551120562000':                                                                                                                                                                                                
 Metadata: 
   title           : DWC-MB44iALPR - Parking Lot LPR 
 Duration: N/A, start: 0.438144, bitrate: N/A 
   Stream #0:0: Video: h264 (High), yuvj420p(pc, bt709, progressive), 2560x1440 [SAR 1:1 DAR 16:9], 7 fps, 30 tbr, 90k tbn, 14 tbc 
[FRAME] 
pkt_dts_time=0.438144 
[/FRAME] 
[FRAME] 
pkt_dts_time=-0.258000 
[/FRAME] 
[FRAME] 
pkt_dts_time=-0.119000 
[/FRAME] 
[FRAME] 
pkt_dts_time=0.015000 
[/FRAME] 
[FRAME] 
pkt_dts_time=0.149000 
[/FRAME] 
[FRAME] 
pkt_dts_time=0.315000 
[/FRAME] 
[FRAME] 
pkt_dts_time=0.449000 
[/FRAME] 
[FRAME] 
pkt_dts_time=0.581000 
[/FRAME] 
[FRAME] 
pkt_dts_time=0.715000 
[/FRAME] 
[FRAME] 
pkt_dts_time=0.881000 
[/FRAME] 
[FRAME] 
pkt_dts_time=1.015000 
[/FRAME] 
[FRAME] 
pkt_dts_time=1.150000 
[/FRAME] 
[FRAME] 
pkt_dts_time=1.317000 
[/FRAME] 
[FRAME] 
pkt_dts_time=1.448000 
[/FRAME] 
[FRAME] 
pkt_dts_time=1.582000 
[/FRAME] 
[FRAME] 
pkt_dts_time=1.716000

DW R&D

March 16, 2019 01:39
I am not using tools.
Connect to rtsp with avformat_open_input of ffmpeg and make AVPacket with av_read_frame. The pts value of AVPacket was positive, but it is negative from the moment.
0

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Negative Presentation Timestamp of RTSP

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