[solved] Merge two videoes with different resolution and bitrates - ffmpeg

[parvares]

Hello I'm trying to merge to videoes with different resolution (1.280x720 vs 640x360 pixels), CRF (constant rate factor: 20 vs 25) and bitrates (average and maximum). I succedeed using Shotcut as converting tool for the first video and MKVToolNix to join the two videoes (the first converted and the second 'original'). I was wondering why using ffmpeg + MKVToolNix the second part of the video (the one not converted) comes pixelated.
I used the exact commands I used for Shotcut to convert the first video:

ffmpeg -threads 0 -i input.mp4 -vf scale=640:360 -sws_flags bilinear -c:v libx264 -b:v 300k -bufsize 2500k -crf 25 -g 125 -bf 3 -c:a aac -ar 44100 -b:a 128k output.mp4

This video comes well, but when I join it to the other video the output is pixalated.

Here are ShotCut commands that succedeed.

[Attachment 58347 - Click to enlarge]

I attach the parameters of the first video (the one to be converted) and the second video.

General
Complete name                            : C:\Users\parvares\Desktop\input.mp4
Format                                   : MPEG-4
Format profile                           : Base Media
Codec ID                                 : isom (isom/iso2/avc1/mp41)
File size                                : 424 MiB
Duration                                 : 38 min 21 s
Overall bit rate                         : 1 545 kb/s
Writing application                      : Lavf58.64.100

Video
ID                                       : 1
Format                                   : AVC
Format/Info                              : Advanced Video Codec
Format profile                           : High@Level3.1
Format settings                          : CABAC / 4 Ref Frames
Format settings, CABAC                   : Yes
Format settings, Reference frames        : 4 frames
Codec ID                                 : avc1
Codec ID/Info                            : Advanced Video Coding
Duration                                 : 38 min 21 s
Bit rate                                 : 1 410 kb/s
Maximum bit rate                         : 1 680 kb/s
Width                                    : 1 280 pixels
Height                                   : 720 pixels
Display aspect ratio                     : 16:9
Frame rate mode                          : Constant
Frame rate                               : 25.000 FPS
Color space                              : YUV
Chroma subsampling                       : 4:2:0
Bit depth                                : 8 bits
Scan type                                : Progressive
Bits/(Pixel*Frame)                       : 0.061
Stream size                              : 387 MiB (91%)
Writing library                          : x264 core 161 r3027 4121277
Encoding settings                        : cabac=1 / ref=2 / deblock=1:0:0 / analyse=0x3:0x113 / me=hex / subme=6 / 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=12 / lookahead_threads=2 / sliced_threads=0 / nr=0 / decimate=1 / interlaced=0 / bluray_compat=0 / constrained_intra=0 / bframes=3 / b_pyramid=2 / b_adapt=1 / b_bias=0 / direct=1 / weightb=1 / open_gop=0 / weightp=1 / keyint=250 / keyint_min=125 / scenecut=40 / intra_refresh=0 / rc_lookahead=125 / rc=crf / mbtree=1 / crf=20.0 / qcomp=0.60 / qpmin=0 / qpmax=69 / qpstep=4 / vbv_maxrate=1680 / vbv_bufsize=8400 / crf_max=0.0 / nal_hrd=none / filler=0 / ip_ratio=1.40 / aq=1:1.00
Color range                              : Limited
Color primaries                          : BT.709
Transfer characteristics                 : BT.709
Matrix coefficients                      : BT.709
Codec configuration box                  : avcC

Audio
ID                                       : 2
Format                                   : AAC LC
Format/Info                              : Advanced Audio Codec Low Complexity
Codec ID                                 : mp4a-40-2
Duration                                 : 38 min 21 s
Bit rate mode                            : Constant
Bit rate                                 : 129 kb/s
Channel(s)                               : 2 channels
Channel layout                           : L R
Sampling rate                            : 48.0 kHz
Frame rate                               : 46.875 FPS (1024 SPF)
Compression mode                         : Lossy
Stream size                              : 35.3 MiB (8%)
Default                                  : Yes
Alternate group                          : 1

General
Complete name                            : C:\Users\parvares\Desktop\1.2.mp4
Format                                   : MPEG-4
Format profile                           : Base Media
Codec ID                                 : isom (isom/iso2/avc1/mp41)
File size                                : 125 MiB
Duration                                 : 40 min 1 s
Overall bit rate                         : 435 kb/s
Writing application                      : Lavf58.64.100

Video
ID                                       : 1
Format                                   : AVC
Format/Info                              : Advanced Video Codec
Format profile                           : High@Level3
Format settings                          : CABAC / 4 Ref Frames
Format settings, CABAC                   : Yes
Format settings, Reference frames        : 4 frames
Codec ID                                 : avc1
Codec ID/Info                            : Advanced Video Coding
Duration                                 : 40 min 1 s
Bit rate                                 : 300 kb/s
Maximum bit rate                         : 2 500 kb/s
Width                                    : 640 pixels
Height                                   : 360 pixels
Display aspect ratio                     : 16:9
Frame rate mode                          : Constant
Frame rate                               : 25.000 FPS
Color space                              : YUV
Chroma subsampling                       : 4:2:0
Bit depth                                : 8 bits
Scan type                                : Progressive
Bits/(Pixel*Frame)                       : 0.052
Stream size                              : 85.8 MiB (69%)
Writing library                          : x264 core 161 r3027 4121277
Encoding settings                        : cabac=1 / ref=2 / deblock=1:0:0 / analyse=0x3:0x113 / me=hex / subme=6 / 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=11 / lookahead_threads=1 / sliced_threads=0 / nr=0 / decimate=1 / interlaced=0 / bluray_compat=0 / constrained_intra=0 / bframes=3 / b_pyramid=2 / b_adapt=1 / b_bias=0 / direct=1 / weightb=1 / open_gop=0 / weightp=1 / keyint=125 / keyint_min=12 / scenecut=40 / intra_refresh=0 / rc_lookahead=30 / rc=crf / mbtree=1 / crf=25.0 / qcomp=0.60 / qpmin=0 / qpmax=69 / qpstep=4 / vbv_maxrate=2500 / vbv_bufsize=12500 / crf_max=0.0 / nal_hrd=none / filler=0 / ip_ratio=1.40 / aq=1:1.00
Color range                              : Limited
Color primaries                          : BT.709
Transfer characteristics                 : BT.709
Matrix coefficients                      : BT.709
Codec configuration box                  : avcC

Audio
ID                                       : 2
Format                                   : AAC LC
Format/Info                              : Advanced Audio Codec Low Complexity
Codec ID                                 : mp4a-40-2
Duration                                 : 40 min 1 s
Bit rate mode                            : Constant
Bit rate                                 : 129 kb/s
Channel(s)                               : 2 channels
Channel layout                           : L R
Sampling rate                            : 44.1 kHz
Frame rate                               : 43.066 FPS (1024 SPF)
Compression mode                         : Lossy
Stream size                              : 36.8 MiB (30%)
Default                                  : Yes
Alternate group                          : 1

Thank you!

[Selur]

Looking at the 640x480 file info:

 cabac=1 / ref=2 / deblock=1:0:0 / analyse=0x3:0x113 / me=hex / subme=6 / 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=11 / lookahead_threads=1 / sliced_threads=0 / nr=0 / decimate=1 / interlaced=0 / bluray_compat=0 / constrained_intra=0 / bframes=3 / b_pyramid=2 / b_adapt=1 / b_bias=0 / direct=1 / weightb=1 / open_gop=0 / weightp=1 / keyint=125 / keyint_min=12 / scenecut=40 / intra_refresh=0 / rc_lookahead=30 / rc=crf / mbtree=1 / crf=25.0 / qcomp=0.60 / qpmin=0 / qpmax=69 / qpstep=4 / vbv_maxrate=2500 / vbv_bufsize=12500 / crf_max=0.0 / nal_hrd=none / filler=0 / ip_ratio=1.40 / aq=1:1.00

and your encoding call:

ffmpeg -threads 0 -i input.mp4 -vf scale=640:360 -sws_flags bilinear -c:v libx264 -b:v 300k -bufsize 2500k -crf 25 -g 125 -bf 3 -c:a aac -ar 44100 -b:a 128k output.mp4

You aimed for the right resolution, max gop size and b-frame count, but ignored everything else,...

Settings like profile, level, vbv, b-pyramid, weight-p, ref count, b-frame count, open-gop, interlaced, mb-tree need to match up.
(https://sites.google.com/site/linuxencoding/x264-ffmpeg-mapping might help a bit)
I'm surprised MKVToolnix doesn't ad least report some warning while appending the files,...

Cu Selur

[jagabo]

Also try adding the --stitchable option if the software will let you.

[parvares]

Thank you Jagabo, thanks Cu Selur, you were right, I had to add a parameter:

-preset fast

which correspons to:
--rc-lookahead 30 --ref 2 --subme 6

ffmpeg -i input.mp4 -vf scale=640:360 -c:v libx264 -preset fast -crf 25 -ar 44100 output.mp4

Optional: -movflags +faststart

Now there is no problem joining the videoes.
MKVToolNix didn't help me with this generic warning:

The codec's private data does not match. Both have the same length (50) but different content. Please make sure that the resulting file plays correctly the whole time. The author of this program will probably not give support for playback issues with the resulting file.