Direct Download - no timestamp

Answered

Maria Smith

January 18, 2023 03:05

We are working to extract large capture downloads.  We have been able to use the Direct download method /hls/{deviceID}.{format}, but the file is received without a timestamp in the metadata. 

Is there an option to ensure the timestamp is received within the file downloaded?

Any suggestions for an alternative method for large file downloads?

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• 

  Andrey Terentyev

  • Network Optix team

  January 19, 2023 15:56 Edited

  Hello,

  Direct download interface has been deprecated. We don't recommend using it.

  Here are interfaces where timestamp is available or can be calcualted.

  1. RTSP streaming. /{deviceId}

  2. HLS streaming. /hls/{deviceId}.m3u. Use the EXT-X-PROGRAM-DATE-TIME tag of a stream.

  The EXT-X-PROGRAM-DATE-TIME tag associates the first sample of a
     Media Segment with an absolute date and/or time.

  for calculating the timestamp, add sequentially a chunk duration to this value

  #EXTM3U
  #EXT-X-VERSION:3
  #EXT-X-TARGETDURATION:6
  #EXT-X-MEDIA-SEQUENCE:194
  
  #EXT-X-PROGRAM-DATE-TIME:2023-01-19T19:02:12.537+04:00
  #EXTINF:5,014000,
  /hls/9587e75c794530f24a430331628bebd6.ts?authKey=9464cb17-dee9-43c0-8f81-cf409d930aaa&hi&sessionID=2&startTimestamp=1674140532537000&durationUsec=5014000&live

  3. /media/{deviceId}.{format} - advised to be used instead of direct download.

  use mp4 format with utc parameter set to true.

  Here is an example of atom

  UUIDTfxdBox:
                                  type: uuid
                                  size: 44
                                  uuid: 6d1d9b05-42d5-44e6-80e2-141daff757b2
                                  version: 1
                                  flags: 0(0x00000000)
                                  FragmentAbsoluteTime: 16741428026210000
                                  FragmentDuration: 83340000

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• 

  Thibault Bougerolles

  February 10, 2023 02:52

  Hello,
  
  Could we have more information on how to retrieve FragmentAbsoluteTime from an HTTP stream? (using FFmpeg preferably).
  I manage to find the information for an HLS stream quite easily, but I can't seem to find a way to retrieve that timestamp data from an HTTP stream using the ffmpeg API or in the command line. (or with any other tool).

  The opened stream always starts with a pts at 0.
  
  The URL we request has this format :
  https://localhost:7001/media/{device_id}.mp4?utc=true 
  
  We do not specify anything else, maybe it is only available if we ask for a pos and endPos?

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• 

  Andrey Terentyev

  • Network Optix team

  February 21, 2023 15:13

  Hello,

  https://localhost:7001/media/{device_id}.mp4?utc=true 

  By the url you've provided the Server will send you endless mp4 file vie HTTP.

  We don't have a ready to use code example, but here is what I've found.

  https://stackoverflow.com/questions/45942670/ffmpeg-c-how-to-get-the-timestamp-in-seconds-since-epoch-that-a-frame-was-tak

   

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