I've been spending some time testing video converters, encoders, editors etc. The good news is that quality & speed have increased pretty much across the board. The bad news is somewhat frequent software bugs or glitches, a lack of standards & controls over your conversions & encoding, & a overall landscape that's more than a bit confusing. I picked up Nero Plat. 2014 & Roxio NXT during the holiday sales, needed to check their capabilities, & so started out trying to answer the question, what's the best software to convert or encode video? Unfortunately I can't pick a clear winner -- for every plus there's a con.
Nero, Roxio, Vegas, Corel, all the ffmpeg & x264 based apps [free & not], have things they're great at, as well as problems or bugs and stuff that just works a bit poorly. I took a look at a converter purely designed to take advantage of Intel & AMD GPUs. I tested 3D conversions. I used an HD video source [AVC 1080p], with output at 1080p & 720p, because that's what these video apps had trouble with a year ago. While I considered it Very important, I did not totally obsess over quality -- if you want absolute top quality you should use a x264 front end like Simple x264 Launcher that lets you do multiple passes at very high quality settings, but that takes more time than I [and most people I think] want to spend encoding a video file. Likewise you can use an Avisinth script to resize your video before (re)encoding using the Simple x264 Launcher -- Avisynth does a better re-size than most anything, but it takes time to write, test, & include it. Everything I tested produced very good quality when you allowed enough bit rate -- again if you want the smallest possible files, meaning lower bit rate settings, use x264 at near highest quality & pay the price of slow encoding. And if you want top quality, lower bit rates [smaller files], & a smaller frame size, use x264 but add AviSynth or VapourSynth to your learning curve. As I said, for every plus there's a minus.
The Software...
I think most video software can be divided into 3, somewhat overlapping categories -- video editing apps, converters, & for lack of a better way to describe them, more video-geek oriented solutions. The one(s) you should use depend on if you lean tech or not, & what your requirements are. If you're after mpg2 to stick on a DVD, IMHO you probably want to use a commercial mpg2 encoder like you'll find in some video editors [e.g. Sony Vegas] -- a good one will let you do Variable Bit Rate [VBR] and pull-down [pull-down makes a 24 fps video file NTSC legal without adding actual frames]. It's harder to say with AVC though -- the open source x264 encoder is one of the very best, but it can be confusing & isn't the fastest, so depending on what you're after you may or may not be able to get more out of an editor or converter you pay for.
The Nero & Roxio suites include separate video converters, but most stand-alone converters are based on open source software, usually ffmpeg or x264. Some are safer because they're self-contained, e.g. most of the converters on GOTD, while others work with Video For Windows [VFW] &/or Direct Show [DS], increasing your capabilities, but adding risk since DS files can conflict with one another. I wouldn't have bought Nero or Roxio just for their converters, & I got each for cheap, but I still like & keep an older version [10] of Nero Recode because I haven't ever found anything quite like it when your source is a DVD [Recode is widely believed to be the successor to DVD Shrink]. VFW applies to codecs so I greatly prefer VFW support -- it may be old tech but it's still very nice to be free to pick whatever output codec rather than having to rely on what's built in. OTOH I try to really, really limit the amount of DS stuff I have installed -- it's not unheard of to spend days if not weeks solving DS conflict problems, though today it's a lot easier with the Win7DSFilterTweaker & the CodecTweakTool, both free at videohelp.com.
Avisynth & the newer Vapoursynth are specialized script interpreters used for manipulating media files. They work with Windows & whatever VFW & Direct Show codecs & files you've got installed, & can act as a go-between, using Windows video playback capabilities to open a file, then passing that data on to a video app that couldn't open that file itself. At the same time you can add functions to a script to resize or otherwise manipulate a video or audio file. I think apps relying on Avisynth for stuff like re-sizing however is on the decline as QT becomes more popular.
What I found testing, & testing ... & testing...
When it comes to encoding AVC, nothing I've tried is completely free of glitches or bugs or gotchas. On the bright side, as long as I kept the bit rate high enough, quality of the encoded AVC file was pretty much excellent no matter what I used. In fact, if you consider price paid into the mix, for conversions &/or AVC encoding I can't pick a favorite that stands out. If you're an optimist, they're all that good -- if you lean pessimistic, they each have enough problems or limitations preventing any one from standing out above the rest.
In the latest version of Nero Plat. [as of today], the video editor may cut out the 1st 8 seconds of your video depending on the encoding settings used. It also can seem to take forever importing your video, and sometimes AVC encoding settings do not actually effect the results, e.g. the bit rate you select may not be the bit rate you get. Nero's converter, Recode, didn't suffer those problems, but you have fewer choices. Using the video editor is the only way to encode Blu-Ray video, & both the video and audio formats available are different between the editor & converter -- in the editor the available audio formats depend on the type of AVC file you're encoding as well. Using GPU assist worked, but only slightly improved encoding times, & using the editor, with GPU assist on it did not obey the bit rate settings I made. When it comes to speed Nero was among the fastest encoding AVC, though the difference is slight, including at HD sizes of 720p & 1080p. Quality tended to be great at higher bit rates -- when the bit rate was at the lower end artifacts were very visible. Bottom line, I picked up Nero Plat 2014 during the holiday sales for just over $20 -- if I had paid over $40 I would be upset.
Roxio NXT is a very mixed bag. Roxio has a bad habit of integrating itself in Windows, to the point I don't plan on adding it to win8.1, & probably wouldn't have added it to win7 if I hadn't already had an earlier version installed -- those deep roots were already there. I've run into the effects & side effects of its installed Direct Show files/filters many, many a time. I originally got Roxio because it does the fastest, neatest job of taking the content in a mpg2 file recorded or saved in Media Center & turning it into a regular mpg2 file without re-encoding. NXT is not the latest version, which is why I picked it up for $14. Comparing encoders, Roxio's video editor isn't really in the mix because you can only use a few AVC templates. Their converter though tends to work very well, is tied for the fastest speed, & only had one irritating idiosyncrasy I came across... it uses the AMD/ATI GPU, & I had to reboot to clear everything out of memory after using & testing GPU assist with the other encoders or converters. AVC quality tended to be excellent except at lower bit rates, where artifacts were very visible.
Corel Video Studio Pro X6 [by Ulead] would not be my choice compared to the editors in Nero & Roxio -- I got it for some other, somewhat unique capabilities, but that's another story. It was a little slower than Nero, & selecting the AVC encoder, making what very few settings are possible, was the worst experience out of everything I tried. Quality OTOH was very good.
A's Video Converter is a bit of an oddball. ATI cards used to come with a minimal video converter that used the card's or chipset's Avivo or Stream capabilities to make encoding very fast. A's Video Converter started as a utility to give you access to the same capabilities but with a better, or at least more capable GUI. Now it's grown up quite a bit, allegedly handling Intel as well as AMD GPUs [I use Virtu, which allows the Intel GPU to help out alongside my AMD card, but A's VC wouldn't use it, which is why I put Allegedly]. It's still developed by a fellow in Japan who doesn't have English skills, so documentation is non-existant -- you play with it for [quite] a while to determine what works & what works best depending on your setup. It was the fastest I've ever tried encoding AVC, but the results were a bit non-standard -- I'm not sure how well they'll play somewhere besides a PC using VLC. Another problem is that 1080p AVC encoded files showed a height of 1088 rather than 1080, though adding a DXVA 1080 resize to the output didn't seem to reduce encoding speed at all, & cured the problem. Quality, at least at higher bit rates was very good.
Most all of the ffmpeg-based encoders can be lumped together, which is what I'll do, calling out the exceptions. The biggest problem, if you want to call it that, is that ffmpeg & the included x264, AVC encoder have LOTS of settings, which are all passed as command line arguments. Software either presents most of them, e.g. the Simple x264 launcher &/or XMedia Recode, & so winds up confusing, or it hides most all settings from you, meaning you can't get the absolute best results no matter what. If you encode a AVC file using XMedia Recode chances are it'll take longer than say one of the converters that's been on GOTD. Since they both use the same encoder, looking at the default quality/speed setting in XMedia Recode shows a possible reason why -- it's set to Medium, with 5 faster settings above it. When I said earlier that A's Video Converter was the fastest I've tried, I didn't include the Tipard Mp4 Video Converter -- that's because the internal settings it makes to or for the x264 encoder are a fair bit different than my other test results... I suspect the Tipard converter's very high speed is a result of those settings, which are likely not as high quality nor as compatible as the competition, since they would surely use those same settings if the results were the same or better. At any rate the Tipard converter is very fast, but be sure to check the results to see if they're up to your standards & play where you need them to.
A constant bit rate [CBR] uses the same level of video compression throughout -- VBR [Variable Bit Rate] means less compression during high motion scenes, more compression when things are relatively quiet. When you use CBR, if you use a high enough bit rate [low enough compression] so that higher motion scenes don't suffer, having a higher bit rate or more bandwidth than you need during quiet scenes doesn't hurt anything -- it just makes the file larger. OTOH the more size or bit rate constraints you have, the more you want to use VBR. Unfortunately often the only way to tell what an encoding app uses, CBR or VBR, is to encode a test file, & then use MediaInfo on it [ http://www.videohelp.com/tools/MediaInfo ]. X264 does let you use VBR, but like everything else about x264's AVC encoding, it's complicated. The more video-geek oriented converters let you access & set those controls -- converters that have been offered on GOTD normally do not. The WinX HD Video Converter Deluxe does have a VBR setting, but using it made no difference in the result.
Of the converters that I picked up on GOTD, speed was pretty much equal among them, & has improved quite a bit at HD frame sizes from just last Spring. One thing I noticed is that with their frequent update/build cycles, bugs being introduced in one version or another was pretty common -- as possible back up or set a restore point or use something like Time Freeze before you install a newer version of your favorite GOTD converter so you can check it out before giving up that old registration key. Another common theme is optional settings for alleged higher quality that don't appear to change anything. And yet another too common bug or glitch is not being able to set the output parameters, & have it stick -- sometimes checking the settings revealed it went back to the preset, while other times I had to check the encoded file to find my settings were all or partially ignored. Sometimes closing the app & restarting it helped when I could make initial settings, but then couldn't modify them. More than one converter made me delete the source file & re-import it before converting it with new settings -- that may be their devs recognizing that there's a problem, causing previously used settings to stick(?).
So why pick up another converter when it's offered on GOTD? Ffmpeg is constantly being updated, so you might get a newer, presumably better, faster version. If a bug was introduced with whatever build, you might also find that fixed. And if you're a bit careful on which ones you install, most [but not all] are very near portable, so adding one you didn't have already can have almost no impact on Windows -- why not add it just in case you find it does something a bit better, or works with an oddball file nothing else likes?
An easy way to check what an install involves is to use Universal Extractor as possible -- it won't work on the GOTD setup file, but it usually will on the trial, & while file versions may be different, the number & location of files should not be. As far as the output goes, very often the free Media Info will not only give you the reported specs of a AVC file, but the command line arguments that were passed to the x264 encoder. Watch out for included downloaders, not because they're bad necessarily, but because like the recent iSkysoft Video Converter Ultimate, there's little way short of a monitored install to reveal the 1000 registry entries it adds. If you're running XP look out for any drivers &/or Microsoft update files -- it's somewhat common to try to install hacked Blu-Ray drivers & MS updates for Blu-Ray compatibility when the setup routine detects XP rather than win7. If you have a Blu-Ray drive &/or have installed software so XP can read the Blu-Ray format, adding updates or drivers for the same purpose can cause conflicts.
About using your graphics card or chipset...
DO Note that using only the CPU tends to mean higher quality results. Part of that is the few tests that have been performed & published comparing the results of whatever operation performed by the CPU vs. GPU, showed the GPU result was lower quality. Another part is that the usual reason to use the GPU is to increase speed, & if that's primarily what you're after, a dev will typically include other speedups as well... if there's some coding trick to make CPU encoding faster, while maintaining quality, it's already being used, so the only shortcuts available probably reduce quality right along with encoding times. A decent sample of what you'll find researching on-line: http://www.behardware.com/articles/828-1/h-264-encoding-cpu-vs-gpu-nvidia-cuda-amd-stream-intel-mediasdk-and-x264.html
A little bit of background... Graphics processors are designed & work differently than CPUs -- otherwise we'd use one or two CPUs & drop the GPUs altogether. :) GPUs are faster & more efficient than CPUs for some types of calculations. OpenCL [Open Computing Language http://en.wikipedia.org/wiki/OpenCL ] is a standard way software can off-load some processes from the CPU, sending them to the GPU instead. It's hard to use OpenCL for video encoding because to work efficiently the CPU has to be ready to receive the data from the GPU's number crunching, but not sitting there idle for long periods of time just waiting for it -- more often than not CPU use goes down quite a bit, offsetting any gains in speed from using the GPU, making it harder to show any sort of overall speed increase. Another complication is that not all GPUs have the same OpenCL performance, e.g. Nvidia cranked OpenCL down several notches in their recent cards, so developers can't count on some sort of baseline speed or capabilities. https://compubench.com/result.jsp
Direct X originally was a way for software to access hardware more directly instead of passing everything through the often several layers in Windows. Once you're talking to the hardware you can add extra functions to that hardware, so what otherwise would mean a bunch of calls to the graphics card/chipset can be accomplished with relatively few sort of shortcut commands. Most video-related software uses DX to take some of the load off the CPU, & like with OpenCL, capabilities will vary depending on the manufacturer & graphics hardware model. DXVA [DirectX Video Acceleration http://en.wikipedia.org/wiki/DirectX_Video_Acceleration ].
Besides DXVA, most video cards & onboard chipsets have their own hardware assist for playing [& sometimes encoding] video -- the electronics & controls involved come into play when the graphics drivers detect you opening a video file or stream. Some of that hardware video acceleration can be accessed by 3rd party software, on cards or onboard chipsets that support it. This stuff ties into the proprietary coding & methods of Intel's Quick Sync, Nvidia's Cuda, & AMD/ATI's Avivo or Stream. And once again capabilities vary by manufacturer & model. AMD in theory at least may have just upped the ante, making the XBox One & PS4 low level interaction with their GPUs available for PC coders.
Now, what all that means to you is that you'll likely get some sort of graphics hardware assist when you're playing or working with video, but how much varies, a lot, based on your hardware, the software you've installed, & the software you're using. It *may* show up if you monitor the graphics hardware with something like GPU-Z, or it may not. http://www.techpowerup.com/gpuz/ It may speed things up, or not. Ffmpeg had Cuda support 1st because that's the hardware the coders used themselves. ATI support in ffmpeg came [much] later, & won't work for me at all if/when overall results are what matters. For me... It does change how AVC files are encoded, though sometimes the difference seems to be just the x264 parameters missing in the MediaInfo window. It does change the amount of CPU use during encoding. It does not reduce the total time required for an AVC encode. It does not show up in GPU use as monitored in something like GPU-Z, though it may well make use of the AMD/ATI Avivo or Stream functions still included in recent cards. I suspect that Avivo/Stream is what a couple of ffmpeg converters use that include a different set of files for AMD/ATI assist than usual. Pavtube & Aunsoft apps have a ATIEnc.dll file -- most ffmpeg apps have ATISpeedUp.dll. I couldn't find any info on that filename, but in the Aunsoft apps turning AMD assist on causes a crash, while in Pavtube it works [according to GPU-Z] but causes 1080p to be encoded at reduced frame height.
