mkv to mp4 transcode results in fast video

[HSV Guy]

I have noticed that when transcoding recent mkv files to mp4 that the video plays back significantly faster than what it should. I have tried transcoding the files to mp4 using both GOTSent and YAMB (off the top of my head I think I only used YAMB to "mux" them back together, I think I used the mkv toolbox GUI to split the file) with the same result. I have also tried an older mkv file and it works ok. I therefore suspect that it is something different between the older and newer mkv files.

I have posted the details of the MKV (and bad MP4) files below - which are from MediaInfo. The only difference I can see between the ok and bad mkv file (that means anything to me) is the good one is 25fps and the bad one is 50fps.

Details of ok MKV

General
Unique ID                        : 190837446784740164631015799390638002086 (0x8F91F49054B130ECDCA41623E4A14FA6)
Format                           : Matroska
File size                        : 1.46 GiB
Duration                         : 1h 1mn
Overall bit rate                 : 3 402 Kbps
Encoded date                     : UTC 2011-06-26 20:24:59
Writing application              : mkvmerge v2.9.8 ('C'est le bon') built on Aug 13 2009 16:16:13
Writing library                  : libebml v0.7.7 + libmatroska v0.8.1

Video
ID                               : 1
Format                           : AVC
Format/Info                      : Advanced Video Codec
Format profile                   : High@L3.1
Format settings, CABAC           : Yes
Format settings, ReFrames        : 4 frames
Format settings, GOP             : N=1
Codec ID                         : V_MPEG4/ISO/AVC
Duration                         : 1h 1mn
Bit rate                         : 2 950 Kbps
Nominal bit rate                 : 3 207 Kbps
Width                            : 1 280 pixels
Height                           : 720 pixels
Display aspect ratio             : 16:9
Frame rate                       : 25.000 fps
Color space                      : YUV
Chroma subsampling               : 4:2:0
Bit depth                        : 8 bits
Scan type                        : Progressive
Bits/(Pixel*Frame)               : 0.128
Stream size                      : 1.26 GiB (87%)
Writing library                  : x264 core 105 r1732 2b04482
Encoding settings                : cabac=1 / ref=3 / deblock=1:0:0 / analyse=0x3:0x113 / me=hex / subme=6 / psy=1 / psy_rd=1.00:0.00 / mixed_ref=0 / me_range=16 / chroma_me=1 / trellis=1 / 8x8dct=1 / cqm=0 / deadzone=21,11 / fast_pskip=1 / chroma_qp_offset=-2 / threads=18 / sliced_threads=0 / nr=0 / decimate=1 / interlaced=0 / constrained_intra=0 / bframes=3 / b_pyramid=2 / b_adapt=1 / b_bias=0 / direct=1 / weightb=1 / open_gop=0 / weightp=0 / keyint=250 / keyint_min=25 / scenecut=40 / intra_refresh=0 / rc=2pass / mbtree=0 / bitrate=3207 / ratetol=1.0 / qcomp=0.60 / qpmin=10 / qpmax=51 / qpstep=4 / cplxblur=20.0 / qblur=0.5 / ip_ratio=1.40 / pb_ratio=1.30 / aq=1:1.00

Audio
ID                               : 2
Format                           : AC-3
Format/Info                      : Audio Coding 3
Mode extension                   : CM (complete main)
Codec ID                         : A_AC3
Duration                         : 1h 1mn
Bit rate mode                    : Constant
Bit rate                         : 384 Kbps
Channel(s)                       : 6 channels
Channel positions                : Front: L C R, Side: L R, LFE
Sampling rate                    : 48.0 KHz
Bit depth                        : 16 bits
Compression mode                 : Lossy
Stream size                      : 169 MiB (11%)

Details of bad MKV

General
Unique ID                        : 225171590909705966843017806474790216097 (0xA96678908FB656FA96333E6CEB9EA1A1)
Format                           : Matroska
File size                        : 1.84 GiB
Duration                         : 1h 1mn
Overall bit rate                 : 4 259 Kbps
Encoded date                     : UTC 2012-02-11 19:51:02
Writing application              : mkvmerge v5.2.0 ('I can't explain') built on Dec 18 2011 18:12:03
Writing library                  : libebml v1.2.3 + libmatroska v1.3.0

Video
ID                               : 1
Format                           : AVC
Format/Info                      : Advanced Video Codec
Format profile                   : High@L4.1
Format settings, CABAC           : Yes
Format settings, ReFrames        : 9 frames
Muxing mode                      : Header stripping
Codec ID                         : V_MPEG4/ISO/AVC
Duration                         : 1h 1mn
Bit rate                         : 3 982 Kbps
Width                            : 1 280 pixels
Height                           : 720 pixels
Display aspect ratio             : 16:9
Frame rate mode                  : Variable
Frame rate                       : 50.000 fps
Color space                      : YUV
Chroma subsampling               : 4:2:0
Bit depth                        : 8 bits
Scan type                        : Progressive
Bits/(Pixel*Frame)               : 0.086
Stream size                      : 1.72 GiB (94%)
Writing library                  : x264 core 120 r2146 bcd41db
Encoding settings                : cabac=1 / ref=9 / deblock=1:0:0 / analyse=0x3:0x133 / me=umh / subme=10 / psy=1 / psy_rd=1.00:0.00 / mixed_ref=1 / me_range=24 / chroma_me=1 / trellis=2 / 8x8dct=1 / cqm=0 / deadzone=21,11 / fast_pskip=1 / chroma_qp_offset=-2 / threads=6 / sliced_threads=0 / nr=0 / decimate=1 / interlaced=0 / bluray_compat=0 / constrained_intra=0 / bframes=8 / b_pyramid=2 / b_adapt=2 / b_bias=0 / direct=3 / weightb=1 / open_gop=0 / weightp=2 / keyint=250 / keyint_min=25 / scenecut=40 / intra_refresh=0 / rc_lookahead=60 / rc=crf / mbtree=1 / crf=18.0 / qcomp=0.60 / qpmin=0 / qpmax=69 / qpstep=4 / ip_ratio=1.40 / aq=1:1.00
Language                         : English

Audio
ID                               : 2
Format                           : AC-3
Format/Info                      : Audio Coding 3
Mode extension                   : CM (complete main)
Muxing mode                      : Header stripping
Codec ID                         : A_AC3
Duration                         : 1h 1mn
Bit rate mode                    : Constant
Bit rate                         : 192 Kbps
Channel(s)                       : 2 channels
Channel positions                : Front: L R
Sampling rate                    : 48.0 KHz
Bit depth                        : 16 bits
Compression mode                 : Lossy
Stream size                      : 84.9 MiB (5%)

Details of bad MKV converted to MP4 (specifically note the length of the video track)

General
Format                           : MPEG-4
Format profile                   : Base Media
Codec ID                         : isom
File size                        : 1.83 GiB
Duration                         : 1h 1mn
Overall bit rate                 : 4 232 Kbps
Encoded date                     : UTC 2012-03-14 10:40:28
Tagged date                      : UTC 2012-03-14 10:40:28

Video
ID                               : 2
Format                           : AVC
Format/Info                      : Advanced Video Codec
Format profile                   : High@L4.1
Format settings, CABAC           : Yes
Format settings, ReFrames        : 9 frames
Codec ID                         : avc1
Codec ID/Info                    : Advanced Video Coding
Duration                         : 42mn 53s
Bit rate mode                    : Variable
Bit rate                         : 5 860 Kbps
Maximum bit rate                 : 36.1 Mbps
Width                            : 1 280 pixels
Height                           : 720 pixels
Display aspect ratio             : 16:9
Frame rate mode                  : Constant
Frame rate                       : 50.000 fps
Color space                      : YUV
Chroma subsampling               : 4:2:0
Bit depth                        : 8 bits
Scan type                        : Progressive
Bits/(Pixel*Frame)               : 0.127
Stream size                      : 1.76 GiB (96%)
Writing library                  : x264 core 120 r2146 bcd41db
Encoding settings                : cabac=1 / ref=9 / deblock=1:0:0 / analyse=0x3:0x133 / me=umh / subme=10 / psy=1 / psy_rd=1.00:0.00 / mixed_ref=1 / me_range=24 / chroma_me=1 / trellis=2 / 8x8dct=1 / cqm=0 / deadzone=21,11 / fast_pskip=1 / chroma_qp_offset=-2 / threads=6 / sliced_threads=0 / nr=0 / decimate=1 / interlaced=0 / bluray_compat=0 / constrained_intra=0 / bframes=8 / b_pyramid=2 / b_adapt=2 / b_bias=0 / direct=3 / weightb=1 / open_gop=0 / weightp=2 / keyint=250 / keyint_min=25 / scenecut=40 / intra_refresh=0 / rc_lookahead=60 / rc=crf / mbtree=1 / crf=18.0 / qcomp=0.60 / qpmin=0 / qpmax=69 / qpstep=4 / ip_ratio=1.40 / aq=1:1.00
Encoded date                     : UTC 2012-03-14 10:40:32
Tagged date                      : UTC 2012-03-14 10:41:37

Audio
ID                               : 1
Format                           : AAC
Format/Info                      : Advanced Audio Codec
Format profile                   : LC
Codec ID                         : 40
Duration                         : 1h 1mn
Bit rate mode                    : Variable
Bit rate                         : 163 Kbps
Maximum bit rate                 : 201 Kbps
Channel(s)                       : 2 channels
Channel positions                : Front: L R
Sampling rate                    : 48.0 KHz
Compression mode                 : Lossy
Stream size                      : 72.0 MiB (4%)
Encoded date                     : UTC 2012-03-14 10:40:28
Tagged date                      : UTC 2012-03-14 10:41:37

In the above details you can see that the MP4 thinks the video is only 43 minutes long, compared to the 61 minutes it should be, and it still says that it is 50 fps. I have tried opening it another PC, using both media info and an actual video player (vlc & WMP) with the same effect.

The factor/ratio of 43 to 61 is 0.704 or 1.4186 which doesn't seem to line up with anything that makes sense (e.g. 25(fps) to 30 or 30 to 50 or anything else I could think of).

Any ideas on what may be causing this? In case you ask, the reason for transcoding the file is because the 50fps mkv files won't play on my xBox (using Windows Media Center) whereas older ones work fine.

[bat999]

Any ideas on what may be causing this?

Hi
Your ok mkv file has constant frame rate 25fps.
Your bad mkv file has variable frame rate 50fps.
Your bad mp4 file seems to have constant frame rate 50fps.

Maybe you need to make an mp4 file with constant frame rate 25fps.
Do you know how to do this?

[HSV Guy]

Maybe you need to make an mp4 file with constant frame rate 25fps.
Do you know how to do this?

I did a quick google search (and this thread very helpfully came up as the first result ) but wasn't able to find anything, so I'll say no.

Were you able to tell that one of the mkvs was vfr and the other was vfr from the MediaInfo details (I couldn't (and still can't) see anything in the mediaInfo details that show this).

[bat999]

Were you able to tell that one of the mkvs was vfr and the other was vfr from the MediaInfo details (I couldn't (and still can't) see anything in the mediaInfo details that show this).

Hi
Yes, information is from MediaInfo.

 Frame rate mode  : Variable

so I'll say no.

If you do want to make an mp4 file with constant frame rate 25fps...
Use latest FFmpeg build from here --> http://ffmpeg.zeranoe.com/builds/

For first attempt...
Try a command like this:-

 ffmpeg -i filename.mkv -vsync 1 -r 25 -c:v libx264 -c:a copy filename.mp4

[HSV Guy]

Not wanting to sound like someone who can't help themselves, but when I run the below command I get an error about the codec frame size not being set and another error (which I assume is due to the first one). I've done a brief search on codec frame size is not set and couldn't find anything that appeared to be useful (and the hex code returns nothing).

ffmpeg -i "E:\Input.mkv" -vsync 1 -r 25 -c:v libx264 -c:a copy "E:\Output.mp4"

[mp4 @ 0000000003E9FA50] track 1: codec frame size is not set
Output #0, mp4, to 'Output.mp4':
  Metadata:
    creation_time   : 2012-02-17 00:52:16
    encoder         : Lavf54.2.100
    Stream #0:0(eng): Video: h264 (![0][0][0] / 0x0021), yuv420p, 1280x720 [SAR
1:1 DAR 16:9], q=-1--1, 25 tbn, 25 tbc (default)
    Stream #0:1: Audio: ac3 ([165][0][0][0] / 0x00A5), 48000 Hz, stereo, 192 kb/
s (default)
Stream mapping:
  Stream #0:0 -> #0:0 (h264 -> libx264)
  Stream #0:1 -> #0:1 (copy)
Could not write header for output file #0 (incorrect codec parameters ?)

Any thoughts on what may be the issue?

[bat999]

Any thoughts on what may be the issue?

Hi
Perhaps it's the AC-3 soundtrack that's upsetting things.
Try again with this command:-

ffmpeg -i filename.mkv -vsync 1 -r 25 -c:v libx264 -c:a aac -strict experimental -q:a 100 -ac 2 -ar 48000 filename.mp4

[HSV Guy]

Thanks for that bat999. That command worked. I haven't checked it on my xbox, but playing the converted mp4 on my PC it look like it should be good.

[bat999]

... it look like it should be good.

If it is OK, then it will be easy to use latest WinFF from here ---> http://winff.org/html_new/
And make your own preset ---> http://code.google.com/p/winff/wiki/HowToMakePresets

EDIT
And if you do use WinFF...
you can change this:-

-c:a aac -strict experimental -q:a 100 -ac 2 -ar 48000

to this:-

-c:a libfaac -q:a 100 -ac 2 -ar 48000