Re: Get camera timestamp from rtsp stream.

[Антон Шаров]

Hi, Anand!
 
Thank you so much for your reply!
 
The thing is I don’t need RTP, I need exact camera(server) capture time of a frame.
Ideally, I need capture time for each frame, but probably for some keyframe of mp4 file
(first frame of this video file?) would be ok also. I’m trying to use my custom appsink,
smth like
appSink.NewSample += AppSink_NewSample;
 
splitmuxsink["sink"] = appSink;
splitmuxsink["max-size-time"] = 3000000000;
splitmuxsink["async-finalize"] = false;
 
private static void AppSink_NewSample(object o, NewSampleArgs args)
        {
            if (o is AppSink aps)
            {
                var sample = aps.PullSample();
                var buf = sample.Buffer;
                buf.Map(out var info, MapFlags.Read);
                var ts = buf.GetReferenceTimestampMeta();// !!!!!!
                buf.Unmap(info);
            }
        }
I don’t quite understand whether it is possible to have needed (3 sec. in this case) mp4 file in
whole buffer, for which I can use GetReferenceTimestampMeta() which return me timestamp
for this buffer (hence for  whole file, hence for keyframe). But on practice with my custom sink
I got some weired chunks in buffer and  GetReferenceTimestampMeta returns null (not null exactly,
but some useless info where needed timestamp = 0).
 
I believe this ideal approach won’t work (because appsink is not seekable), but at least it looks like
desired solution.
 
In case of default sink (filesink), I need
*  change file name, which somehow seems to be possible but is buggy on .net library, but at least it is seems to possible;
*  get timestamp of the first frames (buffer) of newly created file. Ideally I would like to name newly created file with timestamp_value.mp4.
 
 
  
>Среда, 19 июля 2023, 12:37 +03:00 от Anand Sivaram <aspnair at gmail.com>:
> 
>Hello Anton,
> 
>The RTSP media is coming as separate RTP streams for each video and audio.  They must be having only usual RTP parameters like timestamp, sequence number and payload type.
>That too RTP timestamps are initialized randomly as per standard, so the timestamps on video and audio streams have no relation at all.
>If you are planning to read the time using some OCR software from the video frame, then you will have to decode H.264 and the typical granularity is 1sec.
> 
>Are you using the "format-location" callback signal in splitmuxsink with which you can generate custom filenames with timestamp and any prefix.  It is not available on gst-launch, but it is definitely available on C and Python.
> 
>Thanks and Regards
> 
>Anand
>   
>On Mon, 17 Jul 2023 at 15:36, Антон Шаров via gstreamer-devel < gstreamer-devel at lists.freedesktop.org > wrote:
>> 
>>Hi.
>> 
>>I’m given rtsp stream from camera, where each frame has capturing timestamp.
>>Connection strin looks like rtsp://{usr}:{pwd{@ip_addr/onvif/media?profile=Profile1
>>I need to store this data for some time and provide search access for this data, either return closest (exact) frame for provided timestamp or return mp4 file which containts this closest frame. My first pipeline is   rtsp ! h264depay ! h264parse ! splitmuxsink  location=… max-time-size=10seconds (for example), when I save new file via splitmuxsink, I’m some how need to get camera timestamp
>>for first frame of video (or key frame) and maybe store this mp4 file as timestamp.mp4 (or save ts for later in some db, for example).
>> 
>>Other approach is to use jpegenc and to store each frame with it’s timestamp, but I don’t know how to obtain timestamp for jpeg buffer (rtsp ! decodebin ! jpegenc ! appsink). But  I assume  that this won’t be effective solution in terms of CPU and storage usage, and better to store mp4 files.
>> 
>>So, in both cases I don’t know how to get reference-timestamp-meta for needed buffer.
>> 
>>Can someone help me? 
>> 
>>PS: I use C# wrapper, namely gstreamer-sharp, but I don’t think it is relevant for this problem.
>> 
>>Thanks in advance.
>> 
>>--
>>С Уважением,
>>Шаров Антон
 
 
--
С Уважением,
Шаров Антон
 
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