MKV to MP4 doubles file size?

So I got a cheap Viewsonic G Tablet. Decent price for awesome hardware. So to make a long story short I'm trying to convert some of my videos to different formats (primarily MKV to MP4) and even converting a 720p MKV to 720p MP4 the size of the file goes from say 500MB to like 1.2GB! Same resolution and everything...why is that? Is MKV that well compressed? Any suggestions?

And to add to this the ONLY reason I have an issue with the size is not due to space but due to the file system Android uses...FAT32...so therefor I'm limited to 4GB size for a movie...converting a 3.5GB 720p MKV movie to a 6.5GB MP4 just doesnt sit right.

Anyways, thanks to anyone that can offer some insight here, the great Google machine isnt working!...

you shouldnt need to convert... it should play mkvs... just need the right software... i would look for hte right software to playback mkvs and confirm it doesnt play before re encoding it...

mkv and mp4 are just containers... you have to pay attention to what codec you are encoding to... mpeg4? xvid? h.264? your mkv is most likely h.264 and your mp4 might be xvid/mpeg4... h.264 has higher better compression and supports higher bitrates than just xvid...
check videohelp or doom9 video guides for more info...

Bookmage said:

mkv and mp4 are just containers...

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+1 mate, I still have horrid memories of the time when I argued with two people, one of which JUST WENT THROUGH C-C-C-COLLEGE CLASSES ON PRECISELY VIDEO EDITING AND ALL THAT, and were suggesting I rename my file to a .avi extension because "it always works" even though the 4-5 different video players I tried themselves had no problem opening or outputting the video and audio. (Problem was that my laptop was too weak with Intel graphics and a Pentium Dualcore to output video data over 50'+ of unamplified VGA cabling that split out to two projectors. Videos were chugging/skipping a lot of frames AND lagging, and video and audio were horribly unsynchronized as a result; this did not happen when my lappy was not plugged into their system)

Also, what bitrate are those movies at?

(ps. a great place for video related help is at http://forum.doom9.org/)

Well I know that the profiles used are what makes the differences, what is it..."Format Profile"...my G Tablet can do low and medium profiles...but can't do "format profile - high"...and this IS a hardware limitation apparently and not software. Ive gotten xyplayer, rockplayer, and all the other media software that DOES support MKV, but again, all my MKV's are 1080p "High" format and the Tegra 2 simply can't do that.

I'm using imTOO converter right now, trying the H.264/MP4 AVC profile. Thats the right one right? Even then though file sizes are large...I converted the movie "The Crazies" that was 720p 8000k High Profile to a 1024x568 resolution at 6000k medium profile and the movie went from 4.3GB to 3.8GB...smaller sure, but at a much lower resolution and bitrate with a bump down in the profile I was expecting a bit smaller file. Is a low drop in size from the source file like this normal?

I dont know guys...just seems odd.

JoeUser said:

I converted the movie "The Crazies" that was 720p 8000k High Profile to a 1024x568 resolution at 6000k medium profile and the movie went from 4.3GB to 3.8GB...smaller sure, but at a much lower resolution and bitrate with a bump down in the profile I was expecting a bit smaller file.

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Bitrate is the only determining factor in file size. Unless you changed the duration of the film, I'm not sure why you would have expected a smaller file size than what you achieved using 6000kbps. Without taking audio into consideration, if you went from 8000kbps to 6000kbps (25% decrease), then your resulting file would have been exactly that much smaller (75% of the original size).

6.0mbps seems a tad high for a 1024x568 video you'll be playing on a tablet. By "a tad high" I of course mean "insanely high". You should be able to reduce the bit rate significantly without noticeable degradation. Better yet, encode using constant quality as opposed to encoding to a constant bit rate.

They are both high. For the devices you are using, you should probably limit it to a maximum of 1024kbps (and even this is slightly high). Don't resize the dimensions of the video -- if they are originally 1280x720 for example, then keep it at that always. Resizing video dimensions will NOT reduce the file size (and this is due to the nature of how the video codecs work).

If I were you, I would give 500kbps a try and see how the quality is on your devices. Thank me for the glorious diskspace savings later.

1500 Kbps for a transcoded MKV (assuming it's h.264 format video and AAC audio at about 128-192 Kbps) is typical for such results.

And obviously, HandBrake is the tool to use, there's nothing else out that can really touch it for quality and usefulness (unless you're a command line wizard and can do all that stuff with the x264 CLI itself). No offense, but that imTOO encoder (and pretty much every single product that company spews out) is a piece of shit, in almost all respects. HandBrake leaves it in the dust...

I'd say toss the MKV into HandBrake, adjust the resolution up or down as required to get the 1024 pixel wide (or less, which will scale up a bit just fine), leave the setting for video encoding with x264 and the Constant Quality factor at 20 for a test encode (a single chapter from a DVD, a small video file, or even a chunk of a video clip based on the seconds, like an A-B section), the default AAC audio is 160 Kbps, and then see how that looks. If the G-Tablet chokes a bit or whatever, try the same encode but change the video encoding from Constant Quality to Average Bitrate of 1500 Kbps and leave everything else the same, encode and check the results.

I actually use 1000 Kbps for my video transcodes for several devices, looks fine to me. It's a smaller screen device and I'm encoding specifically for it (whichever it happens to be) so I don't care about it being full bitrate full resolution stuff even if the device makes the claim that it can play the file at full resolution, etc).

If you've got 1280 pixel wide HD content there's just no reason to encode to that resolution for a given device unless your intention is to actually use an output like HDMI if the device supports it. Not all do but someday they probably will; I just encode for now...

um, you could look at the max settings on an ipad and use that for reference... I remember reencoding my rips to xvids optimized for ipod video using the tv out... they looked fine on the ipad...

Cerulean said:

Don't resize the dimensions of the video -- if they are originally 1280x720 for example, then keep it at that always. Resizing video dimensions will NOT reduce the file size (and this is due to the nature of how the video codecs work).

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If you encode to a constant bit rate, downscaling the video prior to encoding will diminish video quality less significantly than at 1280x720. Assuming a constant quality encode, the lower the resolution, the fewer bits will be required to encode it. A 1000kbps video file at 1280x720 will have significantly fewer artifacts than a 1000kbps video at 1920x1080. There is no reason not to downscale unless the intention will be to output it to an HD display. If you're just going to watch it on the tablet's display, then downscale.

Just remux it instead of trying to transcode it. http://www.afterdawn.com/guides/archive/convert_mkv_to_mp4_for_ps3.cfm

Avidemux can remux the audio/video streams from an MKV container to an MP4 container with minimal muss and fuss. Select the source file, select the audio and video streams, select the output container, and you're pretty much done.