How to decrease the file size?

[socrates]

I have this file with me
Video
ID : 1
Format : AVC
Format/Info : Advanced Video Codec
Format profile : High@L4.1
Format settings, CABAC : Yes
Format settings, ReFrames : 5 frames
Codec ID : V_MPEG4/ISO/AVC
Duration : 1h 52mn
Bit rate : 4 685 Kbps
Width : 1 280 pixels
Height : 690 pixels
Display aspect ratio : 1.85:1
Frame rate mode : Constant
Frame rate : 23.976 fps
Color space : YUV
Chroma subsampling : 4:2:0
Bit depth : 8 bits
Scan type : Progressive
Bits/(Pixel*Frame) : 0.221
Stream size : 3.69 GiB (74%)
Language : English
Default : Yes
Forced : No

Audio
ID : 2
Format : DTS
Format/Info : Digital Theater Systems
Mode : 16
Format settings, Endianness : Big
Codec ID : A_DTS
Duration : 1h 52mn
Bit rate mode : Constant
Bit rate : 1 509 Kbps
Channel(s) : 6 channels
Channel positions : Front: L C R, Side: L R, LFE
Sampling rate : 48.0 KHz
Bit depth : 24 bits
Compression mode : Lossy
Stream size : 1.19 GiB (24%)
Language : English
Default : Yes
Forced : No

The file size around 5.5GB I want to reduce it to around 3GB. The converter I use, TEncoder, changes the video to h264. Does that change the quality? If so, please suggest a technique. Thanks in advance

[hech54]

Does that change the quality?

Reduction in file size reduces(changes) quality.
The End.

[johns0]

Just keep it the same size and burn it to discs which are very cheap or put it on a harddrive which are cheap to buy,in other words don't be so cheap.

[videobruger]

Use an audio bitrate of 256/128 kb/s and a video of 3500 kb/s. Make a 2 min clip and see what you think.

[socrates]

Thank you videobruger for a sensible reply...

[ndjamena]

Format : AVC
Format/Info : Advanced Video Codec
Codec ID : V_MPEG4/ISO/AVC

The converter I use, TEncoder, changes the video to h264.

AVC = H.264 = MPEG4 Part 10

It's all the same codec with different names.

http://en.wikipedia.org/wiki/H.264/MPEG-4_AVC

There are people in the world who think X264 and h.264 are different codecs...

[sanlyn]

The file size around 5.5GB I want to reduce it to around 3GB. The converter I use, TEncoder, changes the video to h264. Does that change the quality?

Yes. It involves re-encoding, which always lowers quality. The extent of lowered quality depends on how the size reduction is done.

Thank you videobruger for a sensible reply...

That's one sensible way of doing it. There are others. hech54's response is also sensible. You should know that all video encoding of this type (h264, MPEG, DivX, etc.) is lossy compression. Lossy means that each successive re-encode loses more and more video data. It is not like ZIP or RAR compression, which is lossless (lossless means that what goes in is what comes out). Re-encoding is not lossless.

[jagabo]

file size = bitrate * running_time

Since the running time is fixed for a particular video, if you want a smaller file use a lower bitrate.

And that smaller file size doesn't come for free. You will pay for it with image quality.

[Hoser Rob]

Just keep it the same size and burn it to discs which are very cheap or put it on a harddrive which are cheap to buy,in other words don't be so cheap.

That's also a very sensible reply ... ahh, noobs who don't know what to ask for and insult people who don't say what they want to hear.

And you're definitely going to lose quality. It's already been re encoded once.

[socrates]

Just keep it the same size and burn it to discs which are very cheap or put it on a harddrive which are cheap to buy,in other words don't be so cheap.

That's also a very sensible reply ... ahh, noobs who don't know what to ask for and insult people who don't say what they want to hear.

And you're definitely going to lose quality. It's already been re encoded once.

Please read my query before commenting
I "know" that I am going to lose quality if I shrink the file. My query is regarding the codec substitution by encoder.
If you don't have anything to write, please don't write. Please don't around paternalizing "noobs"
Now, lets leave at that and move on....

[sanlyn]

There's no codec substitution. Your source is h264. Your output is apparently going to be re-encoded to h264 unless you specify something else.

[poisondeathray]

<Delete>

[hello_hello]

You could get the file size down quite a bit without touching the video. The audio on it's own is around 1.2GB. If you convert the audio to mutichannel AC3 at 384kb per second (for example), that'd reduce the total file size by nearly 1GB. If you downmix the audio to stereo AAC and use a bitrate of 128kb per second, that should take the file size down by a little over 1GB.

Unless you really need it to be 3GB I'd go that route and settle for the resulting file size. If you do need to reduce it further then you'd need to re-encode the video too, using an average bitrate of around 3700 Kbps (assuming my calculations are correct and you downmix the audio to stereo). Currently it's 4685 Kbps. You may or may not notice a loss in quality. It depends how much the video was compressed to begin with.
I use a quality setting for x264 encoding rather than specifying a bitrate. Sometimes, for the quality setting I generally use (which is CRF18) the bitrate of the encoded version is slightly higher. Sometimes it's a lot higher. Sometimes it's also a lot lower. It depends how hard the video is to (re)compress. When you specify a bitrate you're basically specifying the quality in advance, but you don't know what it'll be.

You can use Handbrake or Vidcoder for re-encoding while specifying a bitrate for 2 pass encoding. Chances are TEncoder will do the same (I've never used it myself).



Under the audio tab you'd configure it to downmix the DTS audio to stereo AAC with a bitrate of 128. If you increase the audio bitrate, reduce the video bitrate accordingly, but if my math is correct a video bitrate of 3700kbps and an audio bitrate of 128kbps should give you a file size of 3GB, or very close.

You can choose an average bitrate without selecting 2 pass encoding and while it'll be faster, the quality probably won't be as good, or as consistent. 2 pass encoding uses the first pass to work out how to distribute the bits while the second pass does the encoding.

PS According to my calculations, currently the file with a video bitrate of 4685 and an audio bitrate of 1509 should be around 4.85GB, but you said it was around 5.5GB. Are there other audio steams in the file etc which you didn't list?
Edit: The size of the two streams as displayed by MediaInfo in your first post roughly agree with my math. 3.69GB + 1.19GB = 4.88GB.

I found this. You might want to bookmark it for future reference. It'll give you an idea of bitrates to use if you need to re-encode for a specific file size again. http://www.cole2k.net/bitrate-calculator.html

If you find the encoded version is of an obvious lower quality, you can try reducing the resolution if you don't want to increase the video bitrate. Currently it's 1280x690. You could try resizing to something like 1024x552 (as an example). That should allow the quality to be higher for a given bitrate as there's not as much video to (re)encode.

PPS Handbrake won't copy the video, so if you want to try converting the audio only, give Video to Video Converter a spin while selecting "copy" for the video codec.

[sanlyn]

Good notes. I'm keeping a copy of this one.

[socrates]

Thank you all,
I had to settle with avi format (xvid+ac3). Initially I converted the file to mkv(h264+aac 5.1), but the resultant file didn't play in my standalone bluray player, which supports mkv and mp4. It said bad video codec. So I re-encoded it to avi- xvid--2350 and ac3--5.1 320kbps. File size came down to 2.1GB. There is definite loss of quality but I settled for this.
Thank you all

I used TEncoder for this process

[enim]

FFMPeg users, please give OP a proper command-line for AVC+DTS -> XViD+AC3 for nice quality MKV with proper audio channel mapping for DTS to AC3. I have to go-thru' all pages of FFMPeg Manual & FAQs.

[hello_hello]

Thank you all,
I had to settle with avi format (xvid+ac3). Initially I converted the file to mkv(h264+aac 5.1), but the resultant file didn't play in my standalone bluray player, which supports mkv and mp4. It said bad video codec. So I re-encoded it to avi- xvid--2350 and ac3--5.1 320kbps. File size came down to 2.1GB. There is definite loss of quality but I settled for this.
Thank you all

Does TEncoder let you specify a profile and level for h264 encoding? I assume it uses some flavour of the x264 encoder? If so, check the Bluray player's manual for info regarding what it supports. If you use the appropriate profile and level, you should be fine. High Profile, Level 4.1 is pretty standard these days. If you can't specify a profile and level.... if it was me I'd use something else.

The x264 encoder compresses better than Xvid while retaining more detail. For a given bitrate x264 should give you higher quality, especially at lower bitrates.

[enim]

The x264 encoder compresses better than Xvid while retaining more detail. For a given bitrate x264 should give you higher quality, especially at lower bitrates.

Just in theory, Yes! But, in practice XViD just 20% higher bitrate produces stunning results.

OP is around 2400kbps for 720p, seems OK. OP should try 2800kbps~3000kbps as well as his final target size is around 3GB. At this bitrates there will not be any significant difference between XViD and X264.

I would prefer not be entering in arguments.

[sanlyn]

We'll leave it up to you to help the O.P. encode and find a set top player to handle his Xvid's.

[enim]

Is there anyone here to help me out for the ffmpeg command-line for DTS(5.1) -> AC3(5.1) with proper chanel mapping?