[solved] Convert video changing Scale and Bitrates - Ffmpeg

[parvares]

Hello all, I’m trying to convert a video and change these parameters:

resolution from 1.280x720 to 640x360 pixels
average bitrate: from 1.410 to 300 kb/s
maximum bitrate: from 1.680 to 2500 kb/s
Sampling rate : from 48.0 to 44.1 kHz
Bit rate audio: 128 kb/s

I used this string with ffmpeg vers. 4.3.2-2021-02-20 full build:

ffmpeg -i input.mp4 -c:v -vf scale=640:360 libx264 -b:v 300k -maxrate 2500k -bufsize 2500k -crf 25 -c:a -ar 44100 libfdk_aac -b:a 128k output.mp4

I get the error: “ffmpeg unable to find a suitable output format for scale ‘640:360’ scale 640:360: invalid argument”. Could you help me pleae?

Below is the original file analyzed by MediaInfo, thanks!

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

[ProWo]

ffmpeg -i input.mp4 -vf scale=640:360 -c:v libx264 -b:v 300k -maxrate 2500k -bufsize 2500k -crf 25 -c:a libfdk_aac -ar 44100 -b:a 128k output.mp4

[parvares]

Thanks, ProWo, I'm getting this error

unknown encoder 'libfdk_aac'

I tried to change:

libfdk_aac to
aac

Now I get a warning with the resulting file:

unknown encoder 'libfdk_aac'

[jagabo]

Just "-c:a aac" instead of "-c:a libfdk_aac" then. Or get a version of ffmpeg with libfdk_aac.

[parvares]

Thanks, when I get the output video analyzed by Media info I get 285 kb/s for average bitrate (instead of 300 kb/s) and I don't get the maximum bit rate (2500 kb/s). Does this depend on the bufsize value I set (2500k)? Which value should I change? Thanks very much!

[ProWo]

Use
ffmpeg -i input.mp4 -vf scale=640:360 -c:v libx264 -crf 18 -c:a aac -ar 44100 -b:a 128k output.mp4
instead.

[parvares]

ProWo, thanks a lot. The output gives me now an average bitrate of 486 kb/s, but trying without -crf and -maxrate commands I get exactly the average rate output I need, 300 kb/s.

ffmpeg -i input.mp4 -vf scale=640:360 -c:v libx264 -b:v 300k -bufsize 2500k -c:a aac -ar 44100 -b:a 128k output.mp4

The strange thing is I have to disable my AVG Antivirus, because I get:

ffmpeg\bin\output.mp4: permission denied

[ProWo]

ProWo, thank, I tried, but MediaInfo gives me now an average bitrate of 486 kb/s, and no maxrate.

I know, but the video quality is better. If you want a lower bitrate try higher CRF values (g.e. 20). Recommed values for x264 are 18-23.

[parvares]

I need to concat the output with another video with the same parameters I wrote (average bitrate: 300 kb/s, maximum bitrate: 2500 kb/s). If not I get the concatenated video 'pixelated'...

[ProWo]

I need to concat the output with another video with the same parameters I wrote (average bitrate: 300 kb/s, maximum bitrate: 2500 kb/s). If not I get the concatenated video 'pixelated'...

Then try

ffmpeg -i input.mp4 -vf scale=640:360 -c:v libx264 -b:v 300k -maxrate 2500k -bufsize 2500k -c:a aac -ar 44100 -b:a 128k output.mp4

[parvares]

I tried your string, but when I concat the second video with MKVToolNix it comes grainy and pixalated.
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.
Thanks again for your help!