How to properly reduce MP4 file size without much loss in quality?

[evile1690]

Greetings!

I have a 720p mp4 file that is around 4hrs at 9.02GB.
I want to significantly reduce its size in half without sacrificing video quality.
The file was converted from a 1080p TS file but I have no access to the original.
The reason why I want to do this is because I have another 720p mp4 file that is around 4hrs15min at just 4.27GB.
As it is, the first file is taking up too much space in my drive.
I think this is possible to do using a program like Avidemux but I don't know what settings I should use to properly achieve what I want.

I've attached the mediainfo into the text files.
File 1 is the one I want to convert and File 2 was added as reference of how I want file 1 to be like.

Thanks a lot for anyone who can give me advice.

[mike20021969]

Try halving the bit rate?

[Baldrick]

Easiest: Vidcoder. Use the High Profile preset. Under Settings->Video set the Target size and select 2-pass Encoding. Test convert a short sample.

[Cornucopia]

Regardless, re-encoding to another lossy format, particularly at ~1/2 the bitrate is GUARANTEED to result in a loss in quality. Likely a very noticeable one.

Scott

[evile1690]

Thank you for the replies!!
So I tried using vidcoder and tested it on a one minute clip from the original video.
The clip was around 55.7mb originally and came out as 40.9mb.
I used the high profile setting. I didn't tinker with the settings that much but I put the video on constant quality (to preserve the quality) and lowered the audio to 128kbps.
The conversion time took rather long for a one minute clip though.
I am going to try later to convert the whole thing and hopefully my laptop can handle it.

[hello_hello]

For a given quality setting (ie Handbrake/Vidcoder's constant quality) the bitrate will vary considerably from video to video according to how hard it is to compress. For x264 encoding, the video will be encoded the same way when using constant quality encoding as it is for 2 pass encoding, assuming the bitrate is the same each time. ie If you run a constant quality encode, check the resulting bitrate, then use that bitrate for a 2 pass encode, the two encodes will be virtually the same. Therefore, you'd use the constant quality mode when you want to set the quality, in which case the bitrate required is unknown, or you'd specify a bitrate for a 2 pass encode and the quality becomes the unknown.

If you want a particular file size, use 2 pass encoding while specifying the desired file size/bitrate.
4.5GB might be a bit optimistic for a 720p video over four hours long, but you never know. A slower x264 speed preset should help as it tends to allow the encoder to compress the video a little more efficiently, which means for 2 pass encoding a slower x264 speed preset should increase the quality a little.

[fornit]

Hi,

I've just looked into the mediainfo files in more depth. In those files you can see the encoding settings. And those are very different for file1 and file2:
- bitrate of file1 results from the setting "crf=19.2"
- bitrate of file2 results from the setting "bitrate=2270"

From my experience crf=19.2 for a 1280 * 720 px file will usually result in a bitrate much higher than 2270 kbps. And that is what you see here.

As said in the previous post, you can do a 2-pass conversion with a bitrate limit. If you use ffmpeg you can do that as follows:

ffmpeg -i file1.mp4 -c:v libx264 -preset fast -profile:v high -level 4.1 -pass 1 -passlogfile file1 -b:v 2270k -an -f mp4 -y /dev/null

ffmpeg -i file1.mp4 -c:v libx264 -preset fast -profile:v high -level 4.1 -pass 2 -passlogfile file1 -b:v 2270k -ac 2 -strict experimental -c:a aac -b:a 128k -y smaller_file1.mp4

I'm not sure whether you are limited to x264. I'm just experimenting with x265 - conversion takes longer but filesize is around 40 % lower for the same quality. Or quality is better with the same filesize. So, if you like to experiment you can try the following.

ffmpeg -i file1.mp4 -c:v libx265 -preset fast -x265-params pass=1:stats=file1_265 -b:v 2270k -an -f mp4 -y /dev/null

ffmpeg -i file1.mp4 -c:v libx265 -preset fast -x265-params pass=2:stats=file1_265 -b:v 2270k -ac 2 -strict experimental -c:a aac -b:a 128k smaller_file1_265.mp4

Regards
fornit

[hogger129]

Easiest: Vidcoder. Use the High Profile preset. Under Settings->Video set the Target size and select 2-pass Encoding. Test convert a short sample.

This ^.

Vidcoder also has a "Preview" option and you can see how this looks before you actually do the full encode. A slower x264 setting will also help reduce the file size, but at the cost of longer encode time.

[GuccizBud]

Easiest: Vidcoder. Use the High Profile preset. Under Settings->Video set the Target size and select 2-pass Encoding. Test convert a short sample.

Thanks for this ^, you introduced me to the program as well. There is a definite improvement in quality with this program and these settings over the way I was doing it before, which was with a different program but I mean in terms of the 1-pass vs. 2-pass choice. Where I notice it the most is when I'm recoding a file using the same encoder and file format, just for the purpose of reducing its size, eg. redoing H.264/MPEG-4 AVC but just lowering the bitrate. Before, I would notice a definite reduction in quality (despite not knocking down the transcoded file's bitrate too much and keeping it in the 1,700–2,000 kbps range), most especially noticeable in dark "fades" where I could clearly make out the delineation between the "shades of black" being used for the fade effect. What's interesting now is I actually lowered the bitrate slightly, to 1,500 kbps (I only changed "Target size" to "Target bitrate" in your instructions) and that "steps of luminosity" effect with blacks is no longer present. A lot of these files are in the 7,000–10,000 kbps range and I like to compress them some to keep storage sizes manageable.

The drawback to doing it this way is the obvious one: it takes a lot longer, more than double what I'm used to, but I may get around that by doing batch conversions overnight, to help deal with the impatience factor.

As a point of interest, I installed both the 32-bit and 64-bit versions and ran a benchmark, comparing the two architectures under identical conditions, i.e. same files to convert, using exactly the same settings, and giving VidCoder the run of the computer in both cases ( i.e. not taxing the system otherwise in the meantime) . . . results indicated that using the 64-bit version of VidCoder will knock about 10.8% off the time taken by the 32-bit version, or, to flip it around, using the 32-bit version will add about 12.1% to the time it would take using the 64-bit version. So the 64-bit version it shall be. 

[theewizard]

if 9 gb verus 4 or 5 Gb is too much loss space, on your hard drive
you need a new hard drive

there will always be a loss of quality when reducing a file to 1/2 the size

[GuccizBud]

if 9 gb verus 4 or 5 Gb is too much loss space, on your hard drive
you need a new hard drive

I have two new ones in fact, a 2 TB and a 4 TB, so I don't need a new hard drive, and I also don't need a life coach. Having a decent amount of space does not translate to my not endeavoring to maintain them, and to strive to make the most of the space available to me; in fact I enjoy the upkeep and choose not to be lazy about it. If someone disagrees and wouldn't take the time themselves, that's fine, I won't try to change him, because I don't know anything about him.

there will always be a loss of quality when reducing a file to 1/2 the size

Yes, that's so. Yes indeed .

[theewizard]

Life coach ?
I have neither the time nor the inclination to be a life coach

My statement was based on reading your post about saving space
You want to reduce size and quality of your videos, go ahead..
But if that comment bothered you that much
You have pretty thin skin