Britney Spears' first day as an 'X Factor' judge is NOT a total disaster ... in fact, the pop star has been articulate, encouraging and even funny at times.

Audio has emerged from the first round of auditions in Austin, TX ... where Britney has been dishing out criticism from the judge's table with Simon Cowell, L.A. Reid and Demi Lovato.

It didn't take long for Britney to clash with Demi ... they disagreed with each other on the very first contestant -- one person LOVED it ... the other, not so much.


The crowd is super-pumped -- are you?

So it begins ... Britney Spears just showed up for the first day of filming for Season 2 of "The X Factor" in Texas -- wearing a slim-fitting breast-accentuating pink dress, black heels, and a big smile.

Auditions are set to kick off any minute at the Erwin Center in Austin -- and we're told Britney's fellow "X Factor" judges Simon Cowell and L.A. Reid are there too.


Demi Lovato also showed up ... and got dissed by a fan holding a sign that says, "Go Britney." 

Always tough to be last.

Demi Lovato is exactly 1/15th the celebrity Britney Spears is ... at least in the salary department.

Sources tell TMZ, the 19-year-old singer's raking in just north of a million to join the gang on "X Factor" -- still damn impressive, but face it ... she's no Britney.

Simon Cowell raved about Demi, praising her accomplishments at such a young age ... insisting she will connect with younger viewers.

As we reported, Britney signed a record $15 million deal to work as a judge on the show -- so Demi's getting table scraps ... but in the TV biz, scraps can make you a millionaire.

And just to show how desperately Demi wanted to appease her new "X Factor" overlords -- we're told the former Disney star even structured her upcoming tour around the "X Factor" tapings.

It's the biggest TV news in a long time -- Britney Spears officially signing on to judge the next season of "X Factor" for $15 MILLION -- but Brit looked nervous during the big announcement today.

Simon Cowell made the announcement moments ago at the Upfronts in New York -- publicly unveiling the two newest judges on "X Factor" ... Britney and Demi Lovato.

But unlike Demi, Britney sort of pulled a poker face when Simon called her name.

And when Britney briefly spoke, she sounded nervous, saying, "I am so excited about this whole experience. It's gonna be so much fun and so different from anything I've ever done and I'm ready to find the true star." Demi added, "I am totally stoked to be here!"

Yeah, we bet you are.

Simon Cowell finally announced what we all knew was coming ... Britney Spears is joining "X Factor" ... and so is some other girl.

Cowell just tweeted a photo of himself with Britney, L.A. Reid and the show's 4th judge Demi Lovato (pictured hovering awkwardly over Simon's shoulder).

Simon included a message with the pic -- "Can't believe it's finally happened. Very exciting!"

FOX just made the announcement at the Upfronts in NYC -- where advertisers vie for commercial airtime on TV shows "up front" ... several months before the shows actually premiere.

As we reported, negotiations between Britney and "X Factor" honchos went right down to the wire. Britney's conservators -- her fiance Jason Trawick and her dad Jamie Spears -- signed the $15 million deal on her behalf.


Demi signed her deal immediately before Upfronts as well. It's unclear how much she's getting paid ... but it's fair to assume her paycheck's gonna weigh a lot less than Britney's.

Demi Lovato has officially signed her deal and will be a judge on the next season of "The X Factor" ... TMZ has learned.

According to our sources, Demi will be in NYC tomorrow for the FOX Upfronts to announce her joining the show. 

Demi is scheduled to tour this summer, but our sources say her "X Factor" schedule shouldn't interfere with her touring.

Lovato should have company tomorrow ... as TMZ previously reported, our sources say Britney Spears will be in NYC to announce she's joining the show as well.

Demi Lovato is the front-runner for the 4th seat on the "X Factor" judge's panel, but she hasn't gotten an offer yet ... sources connected with Fox Network tell TMZ.

We broke the story, producers are close to sealing a deal with Britney Spears to fill one of the 2 vacant chairs, but that deal is still in negotiations -- it is NOT closed. We're told both sides expect to reach an agreement and if they do Britney will end up with $15 mil for the season.

Lovato certainly has a fiery personality -- as we reported, she once socked a female back-up dancer in the face during the Jonas Brothers tour.

The other people in contention for the 4th seat are Miley Cyrus, Avril Lavigne, LeAnn Rimes and Fergie. But there have been NO offers made to fill that seat.

Rehabbed Disney queen Demi Lovato says ... she was often seduced into going into fancy nightclubs and high profile restaurants because promoters gave her free drugs and booze.

Lovato finally opened up about her dangerous partying habits to U.K.'s "Fabulous" magazine ... strongly suggesting she was using drugs before entering rehab in 2010.

Lovato never admits to using a specific drug ... but when asked about the rumors of her cocaine use she replied, "I would come off stage in front of 18,000 people and suddenly be alone in a hotel room. I'd come crashing down and would try to find a way to recreate that feeling, to stay 'up'."

The 19-year-old also says it was easy to get her hands on illegal substances ... saying, "Promoters gave me drugs and alcohol in restaurants or clubs. They wanted me to come back so I would be seen there. They were basically kissing my ass."

"I thought they were my friends. I thought I was having fun."

Lovato completed treatment for bulimia, depression and self-mutilation in 2011 ... and says she now understands how lucky she is to have survived her darkest period.

"Being a celebrity can be dangerous. Nobody says 'no'. That's why so many end up overdosing and dying. It could definitely have happened to me."

A year after leaving a treatment facility -- where she sought help for self-mutilation and bulimia -- a happy and healthy Demi Lovato showed off her curvalicious body in a bronze bikini, while soaking up the rays at the beach in Rio de Janeiro on Wednesday.

The 19-year-old has been taking in the sights while on the South American leg of her tour.

Demi Lovato went on a Twitter rampage last night against her former bosses at Disney over an eating disorder joke on one of their shows -- and guess what??? Disney folded and promised to pull the joke from the show. 

Lovato, who left the Disney show "Sonny With a Chance" to battle her own problems with food, took offense to a line from the show,"Shake It Up" -- "I could just eat you up, well if I ate."

Demi sent out a flurry of tweets, one of which read, "I find it really funny how a company can lose one of their actress' from the pressures of an EATING DISORDER and yet still make joke about that very disease..... #nice." 

Word got back to the Mouse House and they responded to Demi in a matter of hours from a PR Twitter account: "We hear you & are pulling both episodes as quickly as possible & reevaluating them ... It’s NEVER our intention to make light of eating disorders!" 

How 'bout that ... The mouse that roared caved to the mouth that roared. 
 

After attending a Halloween party together on Monday night, rumored lovebirds Wilmer Valderrama and Demi Lovato were seen sucking face outside Wilmer's house on Tuesday.

The couple previously dated back in 2010, after Demi split from Joe Jonas.

At 31, Wilmer is 12 years older than 19-year-old Demi.