[SOLVED] [ffmpeg] Preserving frame ratio?

[yetanotherlogin]

Hello,

I used the following ffmpeg command to further compress a video:

ffmpeg -i input.mkv -c:v libx264 -vf scale=720:-2 -pix_fmt yuv420p -c:a aac -b:a 128k -ac 2 -ar 44100 -threads 2 -f mp4 output.mp4

Notice the "-2" which I read somewhere.

Still, the frame ratio isn't preserved (as reported by ffprobe.exe):

Input #0, matroska,webm, from 'input.mkv':
  Metadata:
    ENCODER         : Lavf57.71.100
  Duration: 00:23:55.84, start: 0.000000, bitrate: 9229 kb/s
    Stream #0:0: Video: mpeg2video (Main), yuv420p(tv, top first), 720x576 [SAR64:45 DAR 16:9], SAR 1:1 DAR 5:4, 25 fps, 25 tbr, 1k tbn, 50 tbc (default)

    Metadata:
      DURATION        : 00:23:55.840000000
    Stream #0:1(unknown): Audio: ac3, 48000 Hz, 5.1(side), fltp, 448 kb/s (default)

    Metadata:
      DURATION        : 00:23:55.816000000
      
Input #0, mov,mp4,m4a,3gp,3g2,mj2, from 'output.mp4':
  Metadata:
    major_brand     : isom
    minor_version   : 512
    compatible_brands: isomiso2avc1mp41
    encoder         : Lavf57.83.100
  Duration: 00:00:27.20, start: 0.000000, bitrate: 600 kb/s
    Stream #0:0(und): Video: h264 (High) (avc1 / 0x31637661), yuv420p, 720x576 [SAR 1:1 DAR 5:4], 464 kb/s, 25 fps, 25 tbr, 12800 tbn, 50 tbc (default)

    Metadata:
      handler_name    : VideoHandler
    Stream #0:1(unk): Audio: aac (LC) (mp4a / 0x6134706D), 44100 Hz, stereo, fltp, 128 kb/s (default)

    Metadata:
      handler_name    : SoundHandler

Is there a simple way to tell ffmpeg to not mess with the frame ratio?

Thank you.

[Bernix]

Do you really need scale? It seems to me be redundant.
I think -2 means the resulted height will be even number. (I think) -1 means keep aspect ratio when resizing.
But scaling seem to be here as I mentioned above, try setdar=16/9 to your command line to be sure it is 16/9 set.


Bernix

[yetanotherlogin]

Thanks.

Yes, I do need it, because the output looks weird. The original is at the top:



Here's the command I used:

ffmpeg -i input.mkv -c:v libx264 -vf setdar=dar=4/3 -vf scale=720:-1 -pix_fmt yuv420p -c:a aac -b:a 128k -ac 2 -ar 44100 -threads 2 -f mp4 output.mp4

---
Edit: Found it. It was "setdar=16:9":

ffmpeg -i input.mkv -c:v libx264 -vf scale=720:-1,setdar=16:9 -pix_fmt yuv420p -c:a aac -b:a 128k -ac 2 -ar 44100 -threads 2 -f mp4 output.mp4

Thank you.

[Bernix]

Edit:

I don't know ffmpeg well, but form 16:9 doesn't looks to me good, prefer 16/9. I hope it will works too. Semicolon not sure about properly interpreted.

My bad I though that semicolon is colon Sorry
Bernix

[yetanotherlogin]

There's still a bit of a problem: How can I get rid of the black bars on both sides?

[pandy]

Just don't rescale in first place...

[jagabo]

Why don't you just specify the height along with the width?

-vf scale=720:404

Or if you're too lazy to figure out the height use the negative modulus as indicated earlier.

[yetanotherlogin]

My bad: The black borders are added by the video editor I use before further compressing with ffmpeg.