SQL: eliminate the selection of redundant records that occur within X minutes

Question

DB in use is Firebird 2.1,in case not familiar with here is select statement sql ref:
http://ibexpert.net/ibe/index.php?n=Doc.DataRetrieval
functions ref: http://www.firebirdsql.org/file/documentation/reference_manuals/reference_material/html/langrefupd21.html

i will be happy with any sql slang [i'll convert it].

table schema:

CREATE TABLE EVENT_MASTER (
EVENT_ID                BIGINT NOT NULL,
EVENT_TIME              BIGINT NOT NULL,
DATA_F1                 VARCHAR(40),
DATA_F2                 VARCHAR(40),
PRIMARY KEY (EVENT_ID)
);

the bad news is EVENT_TIME stored as seconds elapsed since the Epoch.

data samples:

"EVENT_ID","EVENT_TIME","DATA_F1","DATA_F2"
25327,1297824698,"8604","A"
25328,1297824770,"8604","I"
25329,1297824773,"8604","A"
25330,1297824793,"8604","A"
25331,1297824809,"8604","1"
25332,1297824811,"8604","GREY"
25333,1297824812,"8604","A"
25334,1297824825,"8604","GREY"
25335,1297824831,"8604","A"
25336,1297824833,"8604","GREY"
25337,1297824838,"8604","A"
25338,1297824840,"8604","1"
25339,1297824850,"8604","A"
25340,1297824864,"8604","A"
25341,1297824875,"8804","GREY" //notice DATA_F1 is different
25342,1297824876,"8604","G"
25343,1297824877,"8604","A"
25344,1297824880,"8604","GREY"
25345,1297824895,"8604","1"
25346,1297824899,"8604","A"
25347,1297824918,"8604","GREY"
25348,1297824930,"8604","YELLOW"
25349,1297824939,"8604","GREY"
25350,1297824940,"8604",""
25351,1297824944,"8604","A"
25352,1297824945,"8604","1"
25353,1297824954,"8604","B"
25354,1297824958,"8604",""
25355,1297824964,"8604","1"
25356,1297824966,"8604","GREY"
25357,1297824974,"8604","1"
25358,1297824981,"8604","GREY"
25359,1297824983,"8604",""
25360,1297824998,"8604","GREY"
25361,1297825003,"8604","2"
25362,1297825009,"8604","G"
25363,1297825018,"8604","GREY"
25364,1297825026,"8604","F"
25365,1297825045,"8604","GREY"
25366,1297825046,"8604","1"

expected output:
distinct "DATA_F1","DATA_F2" rows within X minutes according to EVENT_TIME: like:

25341,1297824875,"8804","GREY"
25327,1297824698,"8604","A"
25328,1297824770,"8604","I"
25332,1297824811,"8604","GREY"
25348,1297824930,"8604","YELLOW"
..etc

Requirements: eliminate the selection of redundant records that occur within 5 minutes [range calcs according to EVENT_TIME column].

last i'm trying follow this pattern:

SELECT * FROM EVENT_MASTER inner join (
SELECT distinct  DATA_F1, DATA_F2 FROM EVENT_MASTER where /*the hard stuff that i need help with: (EVENT_TIME difference within X minutes)*/
) as RemovedDup ON /*EVENT_MASTER.EVENT_ID = problem is i cant select RemovedDup ID otherwise distinct becomes useless!!*/

please help ASAP.

thanks,

EDIT

adding output based on Andrei K. answer:

25331,1297824809,"8604","1"
25327,1297824698,"8604","A"
25342,1297824876,"8604","G"
25332,1297824811,"8604","GREY"
25328,1297824770,"8604","I"
25341,1297824875,"8804","GREY"
25350,1297824940,"8604",""
25352,1297824945,"8604","1" /*bug: time still within 300 seconds, this same as first record*/
25361,1297825003,"8604","2"
25351,1297824944,"8604","A"
25353,1297824954,"8604","B"
25364,1297825026,"8604","F"
25362,1297825009,"8604","G"
25347,1297824918,"8604","GREY"
25372,1297825087,"8604","ORANGE"
25348,1297824930,"8604","YELLOW"
25382,1297825216,"8604","1"
25387,1297825270,"8604","B"
25394,1297825355,"8604","BLUE"
25381,1297825211,"8604","GREY"

EDIT 2: Russell query output: not good output and its very very slow.

1297824698,"8604","A"
1297824770,"8604","I"
1297824809,"8604","1"
1297824811,"8604","GREY"
1297824825,"8604","GREY"
1297824840,"8604","1"
1297824875,"8804","GREY"
1297824876,"8604","G"
1297824880,"8604","GREY"
1297824918,"8604","GREY"
1297824930,"8604","YELLOW"
1297824939,"8604","GREY"
1297824940,"8604",""
1297824945,"8604","1"
1297824954,"8604","B"
1297824964,"8604","1"
1297824998,"8604","GREY"
1297825003,"8604","2"
1297825018,"8604","GREY"
1297825026,"8604","F"
1297825045,"8604","GREY"
1297825046,"8604","1"
1297825063,"8604","1"
1297825079,"8604","GREY"
1297825087,"8604","ORANGE"
1297825094,"8604","GREY"
1297825100,"8604","1"
1297825133,"8604","GREY"
1297825176,"8604","GREY"
1297825216,"8604","1"

EDIT 3:

based on Russell request here is: all rows WHERE DATA_F1 = '8604' AND DATA_F2 = 'GREY'

25332,1297824811,"8604","GREY"
25334,1297824825,"8604","GREY"
25336,1297824833,"8604","GREY"
25344,1297824880,"8604","GREY"
25347,1297824918,"8604","GREY"
25349,1297824939,"8604","GREY"
25356,1297824966,"8604","GREY"
25358,1297824981,"8604","GREY"
25360,1297824998,"8604","GREY"
25363,1297825018,"8604","GREY"
25365,1297825045,"8604","GREY"
25367,1297825059,"8604","GREY"
25371,1297825079,"8604","GREY"
25373,1297825094,"8604","GREY"
25376,1297825116,"8604","GREY"
25378,1297825133,"8604","GREY"
25380,1297825176,"8604","GREY"
25381,1297825211,"8604","GREY"
25384,1297825234,"8604","GREY"
25389,1297825286,"8604","GREY"
25390,1297825314,"8604","GREY"
25391,1297825323,"8604","GREY"
25393,1297825343,"8604","GREY"
25396,1297825370,"8604","GREY"
25397,1297825387,"8604","GREY"
25399,1297825416,"8604","GREY"
25401,1297825436,"8604","GREY"
25402,1297825445,"8604","GREY"
25404,1297825454,"8604","GREY"
50282,1299137344,"8604","GREY"
380151,1309849420,"8604","GREY"

As of this moment [Oct 11,2011 5:00 AM GMT] no absolute correct answer posted, and Andrei K. answer still the best try among others. so sql experts please help me find the solution otherwise i'll start to think that sql is not capable of handling the question requirements! Is it??

remark: event_time is not unique so multiple events can occur at the same second.

Answer 1

If by redundant rows you mean rows registered within 5 minutes and having the same data_f1, data_f2 then try something like this:

SELECT
  e2.event_id,
  e2.event_time,
  e2.data_f1,
  e2.data_f2
FROM
  (SELECT trunc(event_time / 300), data_f1, data_f2, min(event_id) as e_id
   FROM event_master
   GROUP BY 1, 2, 3) e1 
  JOIN 
    event_master e2 ON e1.e_id = e2.event_id