Going to leave here some preliminary findings of mine regarding this issue in case it is relevant to anyone else in the future.
First of all it would seem that at least on a Hikvision ANPR camera model iDS-2CD7A26G0/P-IZHS which is a fairly recent model, the "/ISAPI/Traffic/channels/<ID>/vehicleDetect/plates" call no longer works, in fact it seems to no longer be part of the ISAPI API, this might be ANPR related assuming there is a difference between ANPR and LPR cameras, hard to know without having more than 1 camera to test this on.
While not necessarily the same result as that other API call, there is a way to fetch those records which is to use the API call "/ISAPI/Traffic/vehicleInfoCond", seems to collect the same information with the exception of the picture name.
To test to see if this API call works for your camera, on the program postman do the following:
1) Create a POST call to the address http://YourCameraIpHere:YourHttpPortHere/ISAPI/Traffic/vehicleInfoCond
2) In the Authorization add a Digest Auth with your username and password.
3) On the body select raw then XML and add the following:
XML:
<?xml version="1.0" encoding="UTF-8"?>
<VehicleInfoCond>
<searchID>WhatEverHereDoesntMatter</searchID>
<TimeSpan>
<startTime>2021-03-30T23:00:00Z</startTime>
<stopTime>2021-05-31T22:59:59Z</stopTime>
</TimeSpan>
<maxResults>40</maxResults>
<plateLicense />
<downloadResultPosition>0</downloadResultPosition>
</VehicleInfoCond>
4) Press send.
This will return up to 40 results as set by maxResults (which can be changed to higher or lower values), if the return XML specifies that the totalMatches is greater than the number set in maxResults, one can use downloadResultPosition to get records beyond the limit of the maxResults, so for example if the with the above call one got an XML that contained this:
XML:
<numOfMatches>40</numOfMatches>
<totalMatches>65</totalMatches>
Another call to this api would have to be issued, but this time with downloadResultPosition set to 40, to get the remaining matches.
This is the returned XML from such a call (only 2 records shown for my convenience, since these are fake plate numbers)
XML:
<?xml version="1.0" encoding="UTF-8"?>
<VehicleInfoResult xmlns="http://www.hikvision.com/ver20/XMLSchema" version="2.0">
<downloadID>WhatEverHereDoesntMatter</downloadID>
<responseStatus>true</responseStatus>
<responseStatusStrg>OK</responseStatusStrg>
<numOfMatches>2</numOfMatches>
<totalMatches>2</totalMatches>
<deviceID>ANPR</deviceID>
<MonitoringSiteID />
<VehicleInfoList>
<VehicleInfo>
<indexID>1</indexID>
<plateNo>33-33-AA</plateNo>
<timeSpan>2021-05-31T09:35:19Z</timeSpan>
<country>FRA</country>
<laneID>1</laneID>
<direction>forward</direction>
<believe>83</believe>
<matchingResult>otherlist</matchingResult>
</VehicleInfo>
<VehicleInfo>
<indexID>2</indexID>
<plateNo>44-44-BB</plateNo>
<timeSpan>2021-05-31T09:43:49Z</timeSpan>
<country>SVN</country>
<laneID>1</laneID>
<direction>reverse</direction>
<believe>97</believe>
<matchingResult>otherlist</matchingResult>
</VehicleInfo>
</VehicleInfoList>
</VehicleInfoResult>
This only works for a camera set to "Vehicle Detection" for cameras set to "Mixed-traffic Detection" this does not work since pictures and information saved on "Mixed-traffic Detection" has a different structure and at least on my camera doesn't have things like direction.
As for obtaining the pictures I haven't got that far yet, and there is a chance I might never bother with it, since I currently have it uploading pictures to an FTP server, and it is trivial to match the pictures on the FTP server to the information obtained from the camera. Will however create another post in this thread if I ever end up looking into that ("/ISAPI/ContentMgmt/search" probably plays a part though).
As a side note when something can be accessed from a web page, and there is no readily available documentation to see what API calls should be made, or as is this case the documentation that does exist is shoddy at best, using something like Telerik Fiddler is of great help, since it captures the calls made by the browser, giving a pretty good idea of what one has to do.
Just quoting you, so you get notified as well in case this is still relevant for you.
With that being said, search the API for xml that contains <maxResults> (if you use word search be careful with what software you are using, it might be there and not find it), this should give you an idea what API calls will support what you want, although at least as far as the ISAPI Traffic api documment is concerned "/ISAPI/Traffic/ContentMgmt/dataOperation" seems to be the best contender (doesn't seem work on my camera though).
