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  1. Member
    Join Date: Sep 2010
    Location: India
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    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
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  2. Member hech54's Avatar
    Join Date: Jul 2001
    Location: Yank in Europe
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    Originally Posted by socrates View Post
    Does that change the quality?
    Reduction in file size reduces(changes) quality.
    The End.
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  3. Member johns0's Avatar
    Join Date: Jun 2002
    Location: canada
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    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.
    I think,therefore i am a hamster.
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  4. 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.
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  5. Member
    Join Date: Sep 2010
    Location: India
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    Thank you videobruger for a sensible reply...
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  6. Member
    Join Date: Sep 2012
    Location: Australia
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    Originally Posted by socrates View Post
    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...
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    Last edited by sanlyn; 19th Mar 2014 at 07:26.
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  8. Code:
    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.
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  9. Member
    Join Date: Mar 2011
    Location: Nova Scotia, Canada
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    Originally Posted by johns0 View Post
    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.
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  10. Member
    Join Date: Sep 2010
    Location: India
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    Originally Posted by Hoser Rob View Post
    Originally Posted by johns0 View Post
    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....
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    Last edited by sanlyn; 19th Mar 2014 at 07:26.
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  12. Member
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    Location: Canada
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    <Delete>
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  13. 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).

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    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.
    Last edited by hello_hello; 4th Feb 2014 at 07:48.
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    Last edited by sanlyn; 19th Mar 2014 at 07:27.
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  15. Member
    Join Date: Sep 2010
    Location: India
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    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
    Last edited by socrates; 4th Feb 2014 at 07:23. Reason: adding software used
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  16. 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.
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  17. Originally Posted by socrates View Post
    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.
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  18. 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.
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    Last edited by sanlyn; 19th Mar 2014 at 07:27.
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  20. Is there anyone here to help me out for the ffmpeg command-line for DTS(5.1) -> AC3(5.1) with proper chanel mapping?
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