Newbie question about frame rates.

[MrTorso]

I am using MKVCleaver to demux MKV files so I can re-mix the audio. I then use MKVMerge to mux the raw .264 files and my new AC3 track. When I add the video file to MKVMerge I get the prompt to enter the frame rate. I enter the frame rate as shown in with Mediainfo for the original file. After MUXing I get a different frame rate than what I entered. Is that normal? I really don't see any difference to my eye but the OCD in me makes me want to post and ask here.

This is one example:

Original MKV:

General
Complete name : F:\RiffTrax Projects\XXX\XXX.mkv
Format : Matroska
File size : 2.70 GiB
Duration : 2h 4mn
Overall bit rate : 3 112 Kbps
Writing application : HandBrake 0.9.5
Writing library : libmkv 0.6.4.1

Video
ID : 1
Format : AVC
Format/Info : Advanced Video Codec
Format profile : High@L3.0
Format settings, CABAC : Yes
Format settings, ReFrames : 4 frames
Muxing mode : Container profile=Unknown@3.0
Codec ID : V_MPEG4/ISO/AVC
Duration : 2h 3mn
Bit rate : 2 602 Kbps
Width : 720 pixels
Height : 360 pixels
Display aspect ratio : 2.35:1
Original display aspect ratio : 2.35:1
Frame rate mode : Variable
Frame rate : 23.976 fps
Resolution : 24 bits
Colorimetry : 4:2:0
Scan type : Progressive
Bits/(Pixel*Frame) : 0.419
Stream size : 2.25 GiB (84%)
Writing library : x264 core 112
Encoding settings : cabac=1 / ref=3 / deblock=1:0:0 / analyse=0x3:0x113 / me=hex / subme=7 / psy=1 / psy_rd=1.00:0.00 / mixed_ref=1 / me_range=16 / chroma_me=1 / trellis=1 / 8x8dct=1 / cqm=0 / deadzone=21,11 / fast_pskip=1 / chroma_qp_offset=-2 / threads=3 / sliced_threads=0 / nr=0 / decimate=1 / interlaced=0 / constrained_intra=0 / bframes=3 / b_pyramid=2 / b_adapt=2 / b_bias=0 / direct=1 / weightb=1 / open_gop=0 / weightp=2 / keyint=240 / keyint_min=23 / scenecut=40 / intra_refresh=0 / rc_lookahead=50 / rc=crf / mbtree=1 / crf=15.0 / qcomp=0.60 / qpmin=3 / qpmax=51 / qpstep=4 / ip_ratio=1.40 / aq=1:1.00
colour_primaries : BT.601-6 525, BT.1358 525, BT.1700 NTSC, SMPTE 170M
transfer_characteristics : BT.709-5, BT.1361
matrix_coefficients : BT.601-6 525, BT.1358 525, BT.1700 NTSC, SMPTE 170M

Audio
ID : 2
Format : AC-3
Format/Info : Audio Coding 3
Codec ID : A_AC3
Duration : 2h 4mn
Bit rate mode : Constant
Bit rate : 448 Kbps
Channel(s) : 6 channels
Channel positions : Front: L C R, Surround: L R, LFE
Sampling rate : 48.0 KHz
Stream size : 398 MiB (14%)
Language : English

Remixed MKV:

eneral
Complete name : F:\RiffTrax Projects\XXX\RT-003-XXX_SD.mkv
Format : Matroska
File size : 2.69 GiB
Duration : 2h 4mn
Overall bit rate : 3 109 Kbps
Encoded date : UTC 2011-07-11 03:53:41
Writing application : mkvmerge v4.8.0 ('I Got The...') built on May 24 2011 03:12:58
Writing library : libebml v1.2.0 + libmatroska v1.1.0

Video
ID : 1
Format : AVC
Format/Info : Advanced Video Codec
Format profile : High@L3.0
Format settings, CABAC : Yes
Format settings, ReFrames : 4 frames
Muxing mode : Container profile=Unknown@3.0
Codec ID : V_MPEG4/ISO/AVC
Duration : 2h 4mn
Bit rate : 2 599 Kbps
Width : 720 pixels
Height : 360 pixels
Display aspect ratio : 2.35:1
Original display aspect ratio : 2.35:1
Frame rate mode : Variable
Frame rate : 20.000 fps
Resolution : 24 bits
Colorimetry : 4:2:0
Scan type : Progressive
Bits/(Pixel*Frame) : 0.501
Stream size : 2.25 GiB (84%)
Writing library : x264 core 112
Encoding settings : cabac=1 / ref=3 / deblock=1:0:0 / analyse=0x3:0x113 / me=hex / subme=7 / psy=1 / psy_rd=1.00:0.00 / mixed_ref=1 / me_range=16 / chroma_me=1 / trellis=1 / 8x8dct=1 / cqm=0 / deadzone=21,11 / fast_pskip=1 / chroma_qp_offset=-2 / threads=3 / sliced_threads=0 / nr=0 / decimate=1 / interlaced=0 / constrained_intra=0 / bframes=3 / b_pyramid=2 / b_adapt=2 / b_bias=0 / direct=1 / weightb=1 / open_gop=0 / weightp=2 / keyint=240 / keyint_min=23 / scenecut=40 / intra_refresh=0 / rc_lookahead=50 / rc=crf / mbtree=1 / crf=15.0 / qcomp=0.60 / qpmin=3 / qpmax=51 / qpstep=4 / ip_ratio=1.40 / aq=1:1.00
colour_primaries : BT.601-6 525, BT.1358 525, BT.1700 NTSC, SMPTE 170M
transfer_characteristics : BT.709-5, BT.1361
matrix_coefficients : BT.601-6 525, BT.1358 525, BT.1700 NTSC, SMPTE 170M

Audio
ID : 2
Format : AC-3
Format/Info : Audio Coding 3
Codec ID : A_AC3
Duration : 2h 4mn
Bit rate mode : Constant
Bit rate : 448 Kbps
Channel(s) : 2 channels
Channel positions : L R
Sampling rate : 48.0 KHz
Stream size : 398 MiB (14%)

Like I said to my eyes I don't notice a difference but it doesn't seem right. Any tips? Better tools for the job?

Thanks!!

[rickydavao]

You don't need to do the extra (1st) step of demuxing your MKV. Open MKVMerge and add your original MKV file. You will notice in the middle "window" of MKVMerge that it will display all the tracks making up your original MKV file ... in your case probably only the video and (original) audio. Each will have a checked box on their left. Uncheck the box for the audio, thereby deselecting it for the mux. Now add your new AC3 file to the same project, and go ahead and mux. You should have a new MKV with the original video and new audio, without the original audio.

[MrTorso]

You don't need to do the extra (1st) step of demuxing your MKV. Open MKVMerge and add your original MKV file. You will notice in the middle "window" of MKVMerge that it will display all the tracks making up your original MKV file ... in your case probably only the video and (original) audio. Each will have a checked box on their left. Uncheck the box for the audio, thereby deselecting it for the mux. Now add your new AC3 file to the same project, and go ahead and mux. You should have a new MKV with the original video and new audio, without the original audio.

That is good info. Thanks! There are times though that I need the audio track from the MKV to make my re-mix. Is there any tool you recommend that I could use to just rip or copy the audio only from the MKV file?

[rickydavao]

MKVCleaver should be fine for extracting just the audio from your MKV file, as I believe you can specify which tracks you want to extract (ie. just the audio). Of course, if you extract all of the tracks, you can just delete the wants you don't need (ie. the video) as long as you keep your original MKV file. I think I used to use OGMCleaver (since it also does MKV files) to extract the tracks from my MKV files, but I think that was only because it was quick and very easy to use.

[MrTorso]

Thanks again for the info!!