User Agent: Mozilla/5.0 (Windows NT 10.0; WOW64; rv:36.0) Gecko/20100101 Firefox/36.0 Build ID: 20150122214638 Steps to reproduce: Play a video on YouTube in the HTML5 player on Windows 10 with an Intel HD GPU Actual results: Video is choppy in Firefox, but works fine in Chrome and IE. Expected results: Video playback is smooth

adapterDescription: Intel(R) HD Graphics Family adapterDescription2: adapterDeviceID: 0x0a16 adapterDeviceID2: adapterDrivers: igdumdim64 igd10iumd64 igd10iumd64 igd12umd64 igdumdim32 igd10iumd32 igd10iumd32 igd12umd32 adapterDrivers2: adapterRAM: Unknown adapterRAM2: adapterSubsysID: 00051414 adapterSubsysID2: adapterVendorID: 0x8086 adapterVendorID2: direct2DEnabled: True directWriteEnabled: True directWriteVersion: 10.0.9926.0 driverDate: 1-5-2015 driverDate2: driverVersion: 10.18.15.4079 driverVersion2: info: {u'AzureCanvasBackend': u'direct2d 1.1', u'AzureFallbackCanvasBackend': u'cairo', u'AzureContentBackend': u'direct2d 1.1', u'AzureSkiaAccelerated': 0} isGPU2Active: False numAcceleratedWindows: 1 numTotalWindows: 1 webglRenderer: Google Inc. -- ANGLE (Intel(R) HD Graphics Family Direct3D9Ex vs_3_0 ps_3_0) windowLayerManagerRemote: True windowLayerManagerType: Direct3D 11

I can't reproduce this bug. Can you try using a blank profile ? (Run Firefox with the -p flag).

I just tried on a blank profile - same problem. Can I capture a trace to help you debug?

I don't work on this domain, but it should help developers working on that domain. I'm just checking if this issue is specific to your profile/configuration, since I use Windows 10 myself, and I don't run into this issue. Were you able to reproduce this on your previous OSes ?

Negative - it's specific to the new build of Windows 10 (Tech Preview 2 - Build 9926). I don't recall it being an issue before. Does not occur on the same build with a different GPU. I have a Surface Pro 3, and it might simply be the video drivers. Let's leave it as 'Not Repro' for now and I'll chase it up with Microsoft.

There's a confirmation by Microsoft. > we’re seeing reports of YouTube videos choppy in Firefox 36 on our latest Windows 10 build publicly released yesterday (March 19, 2015).

I had the same problem start happening on the previous build (9926, as reported above) and persist on the one just released (10041) but an updated Intel graphics driver was pushed over Windows Update the day after 10041 was released and now the problem is fixed for me.

Agreed - resolved for my by upgrade to 10041 and a new Intel driver.