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i try to set with a tweek tools other msmpeg2adec.dll
msmpeg2Adec.dll is for the audio in MP4.
msmpeg2Vdec.dll is for the video in MP4. - This is causing trouble.
i tried delete the msmpeg2vdec.dll
I hope you haven't deleted it back then. Check if it is named properly.
Mine works fine.
Probably is not an integrated budget one. 
GMAs and Express Chipsets make problems.
@luucasalves, first check if hardware acceleration has been enabled in settings, because the screenshot says it has been disabled. You may need to unlock the advanced settings first if you haven't already done it. Then check everything that may be disabled in opera:flags. Secondly, don't test Opera's MP4 support with this Twitter video only. Check this:
http://www.quirksmode.org/html5/tests/video.html
If Opera plays all three videos correctly (video and audio), then it's fine. For the H.264/MP4 Opera relies on the system for decoding. For WebM and Ogg/Theora Opera has native support. I haven't come across any other videos with the black screen issue on the web, except those on Twitter posted here. They are MP4. I already shared my suspicions what the cause may be - the msmpeg2vdec.dll. It's just a guess, though. The audio is working, because another DLL is used for decoding the audio streams (usually AAC) within the MP4 - msmpeg2adec.dll and it is related to the GPU process if not the GPU itself.
SwiftShader has nothing to do with video playing. Opera can't use it properly. It's for the WebGL, which I'm still unable to use with my GPU (and probably you won't be).
@babogredac, try the same solution. Same error, although it's an AMD GPU.
An Intel GPU. Why am I not surprised? Check this solution and the topic in general. Hope it helps.
http://forums.opera.com/post/86172
@luucasalves, as leocg said, there is no GPU process - Opera is not using the system codecs at all. Many files on SoundCloud are MP3s, while Spotify streams are Ogg, AFAIK, which Opera natively supports. If you post the "Problems detected" and "Log messages" of opera:gpu, maybe we can find out what is causing this.
@babogredac, check for the GPU process.
Hm, that's strange. What I have found so far is that (in my case) Chrome is using SwiftShader for GL rendering. I think it's falling back to it if there is a problem with the ANGLE renderer (those DLLs we moved). SwiftShader is completely software based, that's why WebGL is working for me in Chrome. If I rename the folder (C:\Users\*\AppData\Local\Google\Chrome\User Data\SwiftShader) so Chrome can't use it, ANGLE is used and I get the same situation as in Opera. I used it with Opera, but unfortunately the whole browser is laggy, glitchy and there is this huge SwiftShader watermark. WebGL works, though. I was almost sure it was the Intel GPUs, but you say yours is not blacklisted...
Anyway, what's with the codecs? They generally do not work or just some specific files you've came across?
Sorry, but you're wrong. I saved it and it plays perfectly fine with both windows media player and media player classic. Yet there's a black screen if I'm trying to watch it on twitter using opera.
This is quite possible. But on my machine every single video that plays audio only with Opera, plays audio only with Windows Media Player. No additional codecs installed. This should lead us somewhere. What certainly I'm wrong about is to expect Opera to act the same way as Windows Media Player. Maybe Opera depends only on the aforementioned native Windows "msmpeg2vdec.dll" for decoding. I clearly see that every opera.exe process (except "Browser") loads this DLL. There are a few other DLLs that may cause trouble, but this is where I would start from. As I said it may be a different version on those machines without the black screen issue in Opera. My version is "6.1.7140.0". Maybe someone without the issue can check the version on his/her machine so we can compare.
Again, these are just thoughts. I may be wrong.
Launcher.exe has been renamed to (replaced by) Opera.exe in v33. If you use this version use Opera.exe.
I rather doubt it, since every version, ie 33.0.1990.43 has its own exe files named Opera. Launcher.exe seems to stay afloat
Yes, my confusion, sorry.
@luucasalves, not all sounds are in MP3 format. I asked specifically for it. Anyway, maybe I should have asked:
Is there a "GPU process" listed in Opera's task manager (Menu > Developer)?
Launcher.exe has been renamed to (replaced by) Opera.exe in v33. If you use this version use Opera.exe.
Glad to hear that and sorry if I caused you trouble. At least someone's problem is solved.
This is definitely a system codec issue and not an Opera one. Here is a link to the video file from the first post:
https://video.twimg.com/ext_tw_video/635619016179101696/pu/vid/720x1280/M6wxwYfuQHPX2mfP.mp4
If you right-click, save it and play it with Windows Media Player, I bet it will play audio only. This is an issue with the Microsoft MPEG video decoder (the default Windows decoder for MP4) not being able to decode the video stream inside the MP4 container. It's common and not isolated to the 64-bit version of Windows. @pete8475, you should have something installed on your other machines, that you don't have on the problematic one - codec packs or media players that install codecs alongside them. Another possibility is that the Microsoft MPEG video decoder is a different version. It's located in the "SysWOW64" folder ("system32" for 32-bit), named "msmpeg2vdec.dll". Even if another decoder is installed, in this case ffdshow, it doesn't mean it's being used, because the Microsoft one has priority. It has to be either disabled manually (take ownership and rename) or via the so called "codec tweaker tools". They allow ffdshow to be selected as decoder for the different containers.
Have you tried this extension?
https://addons.opera.com/extensions/details/gmail-compose
@pete8475, there is audio only or nothing at all on those non working videos?
You are welcome!
WebGL has never worked for me, neither in v27 nor in any other version I have tried. Did it for you? I saw Intel GMA 3150 is blacklisted:
Intel Graphics Media Accelerator 3150 causes the GPU process to hang running WebGL: 305431
Disabled Features: webgl
and enabling "Override software rendering list" didn't help. I didn't bother anymore, because it wasn't crucial for me. Now that you said, I tried Chrome, it states the same thing as above, but WebGL works, which is strange. I'll investigate further. Does opera:gpu state anything considering the Express chipset?
I had the same problem with Intel GMA 3150 (Windows 7 Ultimate, 32-bit). What is even worse is that Opera is not using the proprietary system codecs (like H.264 and MP3) if the GPU process is not running. I managed to find a workaround, though. According to opera:gpu the troublemaker is the EGL.
Copy "d3dcompiler_46.dll", "libEGL.dll" and "libGLESv2.dll" from the installation folder of v27 to the installation folder of the newer version ("libEGL.dll" and "libGLESv2.dll" will prompt for overwrite so rename them). Instead of copying "d3dcompiler_46.dll" from v27 you can also rename the newer version's "d3dcompiler_47.dll" to "d3dcompiler_46.dll".
I'm using v31.0.1889.99 and this enables hardware acceleration for me. No unexpected behaviour or crashes. I hope it will work for you as well, joegd21.