SAN FRANCISCO — Thirty years after revolutionizing portable music with the Walkman for playing cassette tapes, Sony is trying to master the digital media player with the

Tunes sound great and videos look crisp on the device, but Sony still has a lot of work to do to catch up with Apple’s market-ruling iPod. While the X Series brims with features like Wi-Fi and noise cancellation, the limitations and execution problems make it somewhat disappointing overall.

The X Series is sleek and elegant-looking, its black, sparkly rectangular body dominated on the front by a bright, sharp, OLED touch screen. The screen is excellent for watching short videos and viewing photos, and it’s very responsive to finger taps and swipes, making it easy to scroll through lists of pictures, songs and videos and select media for playback.

There are buttons at the top for controlling video and song playback as well – something that came in handy when I was running around blasting songs with the player in my pocket.

As expected with a Sony device, music sounded great on the X Series, and there are plenty of options for adjusting it to your liking. I enjoyed listening to all sorts of tunes on it, from folksy ukulele tracks to hard rock to rap, and I didn’t feel the need to change the sound settings that often.

The device costs $300 or $400, depending on whether you want 16 gigabytes or 32 gigabytes of storage. By contrast, you can buy an iPod Touch for $229 to $399, with memory ranging from 8 GB to 32 GB.

If you get sick of music from your own collection, the X Series has a very good digital FM tuner that I found got a surprisingly good reception.

The device also comes with an application for Slacker Inc.’s personalizable Internet radio service, and a few stations have been pre-loaded. Songs I listened to sounded crystal-clear.

You’ll need to register with Slacker if you want to keep using the application after 30 days – the X Series comes with a Slacker user ID code you can use to create a free Slacker account. From the computer, you can add or delete stations from your list and you can refresh the application’s music over the X Series’ Wi-Fi.

One of my favorite things on the X Series is its built-in noise-canceling feature, which has different settings for use on a bus or train, on a plane or in an office. Within each environment, you can also choose how much noise canceling you want. I tried it out on a busy street, and it quickly hushed the sounds of chatting pedestrians, passing buses and a helicopter whirring overhead.

Sadly, this only works with the earbuds that come with the device. They produce better sound than the average set of freebie earbuds, block ambient noise well even without the noise-canceling feature and fit comfortably in my tiny ears. Still, it would have been nice to use my own headphones.

If you’re planning to put media on the device through the included Media Manager software, you may also run into obstacles. It seemed to have issues with every video I tried to transfer to the X Series. For music, I just opted to sync the device with my tunes through Windows Media Player.

Like Apple Inc.’s iPod Touch and Microsoft Corp.’s Zune, the X Series has Wi-Fi built in – a perk that can really enhance a multimedia player.

However, it’s only half-baked on Sony’s device. With an included application for video-sharing site YouTube, you can watch videos on the small screen – I watched a very crisp clip of Elvis Costello performing in a music store. You’ll have to make sure your Web connection is good, or the video stream will cut out. You can also use Wi-Fi to search for links related to what you’re listening to through Yahoo’s oneSearch or YouTube, or use it to choose podcasts you want to download.

This was all fun, but the party stopped when I tried opening the X Series’ Web browser. Sony really, really needs to go back to the drawing board with this, as it’s a chore to input Web addresses and view resulting Web pages. As expected, I had to stick with mobile versions of Web sites, and even those looked funky sometimes and generally unattractive. You can load regular pages, but it’s painfully slow even with a strong Internet connection.

I did manage to check out and update my status for Facebook using the social-networking site’s mobile page, but each time I got a "lack of resource" message from the X Series before it would load the page.

I also didn’t like how I needed to give the X Series permission to connect to the Internet whenever I tried to perform a function that involved the Web – opening the browser or, say, searching for YouTube videos related to a David Bowie song. Once I okayed this action, the X Series would scan for a list of Wi-Fi hotspots, let me choose one, and then, finally, load the browser or YouTube results.

At least you won’t run out of juice while doing these things: The X Series’ rechargeable battery is rated for a strong 33 hours of music listening time and nine hours of video watching; after a day of listening to music, watching videos and reading news stories online, the player still had plenty of power left.

If great audio is your first – and main – priority, Sony’s X Series may be the one. But if you want a device with features that are more even overall and can surf the Web without major irritations, a name like Apple still sounds better.