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  1. Hello,

    I have some questions:

    1. Using the x264 CRF 18 settings seen below, the color of my output video is somewhat dimmer than the input video, recorded with Fraps (see attached screenshots). Is there a way to resolve this color problem?
    2. How does one enable all Intra frames? Do I set "Number of B-frames" to 0? Or, do I change the "Quantizers Ratio (I:P / P:B)"? Do the values in "Quantizers Ratio" only affect videos encoded with Const. Quantizer?
    3. Is it the case that the fewer the B frames, the higher the quality of a video (and fewer compression)?
    4. What exactly does the lossless option mean? The tooltip in MeGui explains that it changes qp to 0, but how come the lossless video is more compressed than the CRF 18 video and has a smaller overall bit rate? Also, is there a reason why whenever I upload a lossless video to YouTube, it is always messed up?
    5. Is there any restriction on what type of audio file I can mux with a mp4 video, e.g., is a .mp4 audio file encoded with Nero AAC preferred over a LAME mp3? What is the recommended standard?

    CRF 18 settings
    :
    Code:
    program --crf 18 --thread-input --bframes 9 --b-pyramid normal --ref 7 --vbv-maxrate 31250 --subme 9 --partitions all --trellis 2 --output "output" "input"
    Input video (Fraps):
    Code:
    General
    Format                           : AVI
    Format/Info                      : Audio Video Interleave
    File size                        : 917 MiB
    Duration                         : 2mn 38s
    Overall bit rate                 : 48.4 Mbps
    Writing library                  : VirtualDub build 32706/release
    
    Video
    Format                           : FRAPS
    Codec ID                         : FPS1
    Duration                         : 2mn 38s
    Bit rate                         : 48.4 Mbps
    Width                            : 1 280 pixels
    Height                           : 720 pixels
    Display aspect ratio             : 16:9
    Frame rate                       : 30.000 fps
    Bits/(Pixel*Frame)               : 1.751
    Stream size                      : 917 MiB (100%)
    Output video (CRF 18):
    Code:
    General
    Format                           : MPEG-4
    Format profile                   : JVT
    Codec ID                         : avc1
    File size                        : 15.3 MiB
    Duration                         : 2mn 38s
    Overall bit rate                 : 809 Kbps
    Encoded date                     : UTC 2010-03-09 11:45:30
    Tagged date                      : UTC 2010-03-09 11:45:30
    
    Video
    ID                               : 1
    Format                           : AVC
    Format/Info                      : Advanced Video Codec
    Format profile                   : High@L4.1
    Format settings, CABAC           : Yes
    Format settings, ReFrames        : 7 frames
    Codec ID                         : avc1
    Codec ID/Info                    : Advanced Video Coding
    Duration                         : 2mn 38s
    Bit rate mode                    : Variable
    Bit rate                         : 806 Kbps
    Maximum bit rate                 : 1 225 Kbps
    Width                            : 1 280 pixels
    Height                           : 720 pixels
    Display aspect ratio             : 16:9
    Frame rate mode                  : Constant
    Frame rate                       : 30.000 fps
    Resolution                       : 8 bits
    Colorimetry                      : 4:2:0
    Scan type                        : Progressive
    Bits/(Pixel*Frame)               : 0.029
    Stream size                      : 15.3 MiB (100%)
    Writing library                  : x264 core 80 r1376M 3feaec2
    Encoding settings                : cabac=1 / ref=7 / deblock=1:0:0 / analyse=0x3:0x133 / me=hex / subme=9 / psy=1 / psy_rd=1.0:0.0 / mixed_ref=1 / me_range=16 / chroma_me=1 / trellis=2 / 8x8dct=1 / cqm=0 / deadzone=21,11 / fast_pskip=1 / chroma_qp_offset=-2 / threads=3 / sliced_threads=0 / nr=0 / decimate=1 / mbaff=0 / constrained_intra=0 / bframes=9 / b_pyramid=2 / b_adapt=1 / b_bias=0 / direct=1 / wpredb=1 / wpredp=2 / keyint=250 / keyint_min=25 / scenecut=40 / rc_lookahead=40 / rc=crf / mbtree=1 / crf=18.0 / qcomp=0.60 / qpmin=10 / qpmax=51 / qpstep=4 / ip_ratio=1.40 / aq=1:1.00
    Encoded date                     : UTC 2010-03-09 11:45:30
    Tagged date                      : UTC 2010-03-09 11:58:00


    Lossless video
    :
    Code:
    General
    Format                           : MPEG-4
    Format profile                   : JVT
    Codec ID                         : avc1
    File size                        : 14.0 MiB
    Duration                         : 2mn 38s
    Overall bit rate                 : 738 Kbps
    Encoded date                     : UTC 2010-03-14 06:07:28
    Tagged date                      : UTC 2010-03-14 06:07:28
    
    Video
    ID                               : 1
    Format                           : AVC
    Format/Info                      : Advanced Video Codec
    Format profile                   : High 4:4:4 Predictive@L4.0
    Format settings, CABAC           : Yes
    Format settings, ReFrames        : 7 frames
    Codec ID                         : avc1
    Codec ID/Info                    : Advanced Video Coding
    Duration                         : 2mn 38s
    Bit rate mode                    : Variable
    Bit rate                         : 737 Kbps
    Maximum bit rate                 : 1 410 Kbps
    Width                            : 1 280 pixels
    Height                           : 720 pixels
    Display aspect ratio             : 16:9
    Frame rate mode                  : Constant
    Frame rate                       : 30.000 fps
    Resolution                       : 8 bits
    Colorimetry                      : 4:2:0
    Scan type                        : Progressive
    Bits/(Pixel*Frame)               : 0.027
    Stream size                      : 14.0 MiB (100%)
    Writing library                  : x264 core 80 r1376M 3feaec2
    Encoding settings                : cabac=1 / ref=7 / deblock=1:0:0 / analyse=0x3:0x133 / me=umh / subme=9 / psy=1 / psy_rd=0.0:0.0 / mixed_ref=1 / me_range=16 / chroma_me=1 / trellis=0 / 8x8dct=1 / cqm=0 / deadzone=21,11 / fast_pskip=0 / chroma_qp_offset=0 / threads=3 / sliced_threads=0 / nr=0 / decimate=1 / mbaff=0 / constrained_intra=0 / bframes=0 / wpredp=2 / keyint=250 / keyint_min=25 / scenecut=40 / rc=cqp / mbtree=0 / qp=0
    Encoded date                     : UTC 2010-03-14 06:07:28
    Tagged date                      : UTC 2010-03-14 06:19:57
    Thank you for any help,
    Serexl
    Attached Thumbnails Click image for larger version

Name:	input_fraps.bmp
Views:	234
Size:	2.66 MB
ID:	851  

    Click image for larger version

Name:	output_crf18.bmp
Views:	218
Size:	2.66 MB
ID:	852  

    Last edited by serexl; 15th Mar 2010 at 02:36.
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  2. Originally Posted by serexl View Post
    1. Using the x264 CRF 18 settings seen below, the color of my output video is somewhat dimmer than the input video, recorded with Fraps (see attached screenshots). Is there a way to resolve this color problem?
    Small changes are inevitable when converting from RGB to YUV. And the 4:2:0 chroma subsampling of YV12 (used internally by x264 and most other video compression schemes) will cause loss of color resolution. Your sample BMP images don't show anything beyond the expected changes.

    Originally Posted by serexl View Post
    2. How does one enable all Intra frames? Do I set "Number of B-frames" to 0? Or, do I change the "Quantizers Ratio (I:P / P:B)"? Do the values in "Quantizers Ratio" only affect videos encoded with Const. Quantizer?
    Set the Min and Max GOP size to 1.

    Originally Posted by serexl View Post
    3. Is it the case that the fewer the B frames, the higher the quality of a video (and fewer compression)?
    B frames are encoded at lower quality settings. But whether this means lower quality overall depends on how you look at it. For a given bitrate, I and P frames can be encoded at higher bitrates because the B frames are encoded at a lower bitrate. The idea here is that a few frames encoded at lower quality won't be so noticeable because a higher quality frame will come along soon and clean up the picture. So some frames are higher quality, some lower.

    Originally Posted by serexl View Post
    4. What exactly does the lossless option mean? The tooltip in MeGui explains that it changes qp to 0, but how come the lossless video is more compressed than the CRF 18 video and has a smaller overall bit rate? Also, is there a reason why whenever I upload a lossless video to YouTube, it is always messed up?
    Lossless means lossless (although your RGB source will still lose some accuracy because of the RGB to YUV conversion and YV12 chroma subsampling. But x264 always obeys the Min QP setting. So to really get lossless encoding you need to set Min QP to 0 too. The YV12 that comes out of x264 decompression will be exactly the same as the YV12 that went in.

    Originally Posted by serexl View Post
    5. Is there any restriction on what type of audio file I can mux with a mp4 video, e.g., is a .mp4 audio file encoded with Nero AAC preferred over a LAME mp3? What is the recommended standard?
    No, using h.264 video does not restrict the audio. But not all containers support all audio codecs. The MP4 container recently added AC3 audio support but many tools still don't work with it. AAC sounds better than MP3 a low bitrates.
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  3. Member
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    Originally Posted by jagabo View Post
    Originally Posted by serexl View Post
    2. How does one enable all Intra frames? Do I set "Number of B-frames" to 0? Or, do I change the "Quantizers Ratio (I:P / P:B)"? Do the values in "Quantizers Ratio" only affect videos encoded with Const. Quantizer?
    Set the Min and Max GOP size to 1.
    The option is "--keyint 1", IIRC.
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  4. Thank you for the quick and thorough replies.
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