Apologies if this question has been asked. I couldn't find it, but if it has, please let me know and I'll close this out.
I'm attempting a simple scale of a video whose original dimensions are 480x360 and whose target dimensions are 400x300. The video starts as an FLV and eventually needs to end up as an MPEG. I'm using the following command line to do this:
ffmpeg -i user.flv -vf "scale=400:300" user_scaled.mpg
When I play the scaled video in MPEG Streamclip, the scale is correct and the video info shows that the dimensions are 400x300. However, when I play the scaled video in Quicktime, the video is scaled to 478x359. More importantly, FFMPEG, itself, treats the video as being 478x359, so any future commands (trimming, conversion, overlaying, etc) executed on it result in a video of 478x359.
The initial workflow required an FLV to MPEG conversion, but I've tried this with several different in and out formats (FLV -> FLV, FLV -> MPEG, MPEG -> MPEG, etc) all with the same results. As long as I can end up with an MPEG, though, I can deal with however many steps and conversions it would take to get this scaling working.
I'll paste the command-line output below, and a sample input video is also linked below, if you'd like it. Thank you very much for any help.
http://www.monkeydriver.com/dpassera/stack_flv.zip
Command-line output:
ffmpeg -i user.flv -vf "scale=400:300" user_scaled.mpg
ffmpeg version 0.7-rc1, Copyright (c) 2000-2011 the FFmpeg developers
built on May 21 2011 22:13:19 with gcc 4.1.2 20080704 (Red Hat 4.1.2-50)
configuration: --prefix=/usr --libdir=/usr/lib64 --shlibdir=/usr/lib64
--mandir=/usr/share/man --incdir=/usr/include --disable-avisynth
--extra-cflags='-O2 -g -pipe -Wall -Wp,-D_FORTIFY_SOURCE=2 -fexceptions
-fstack-protector --param=ssp-buffer-size=4 -m64 -mtune=generic -fPIC'
--enable-avfilter --enable-libdirac --enable-libgsm --enable-libmp3lame
--enable-libopencore-amrnb --enable-libopencore-amrwb --enable-libx264
--enable-gpl --enable-postproc --enable-pthreads --enable-shared
--enable-swscale --enable-vdpau --enable-version3 --enable-x11grab
--disable-yasm --enable-filters --enable-filter=movie
libavutil 50. 40. 1 / 50. 40. 1
libavcodec 52.120. 0 / 52.120. 0
libavformat 52.108. 0 / 52.108. 0
libavdevice 52. 4. 0 / 52. 4. 0
libavfilter 1. 77. 0 / 1. 77. 0
libswscale 0. 13. 0 / 0. 13. 0
libpostproc 51. 2. 0 / 51. 2. 0
[flv @ 0x11dd3b30] Estimating duration from bitrate, this may be inaccurate
Input #0, flv, from 'user.flv':
Metadata:
duration : 5
videocodecid : 2
audiocodecid : 6
canSeekToEnd : true
createdby : FMS 4.0
creationdate : Mon Oct 31 11:43:44 2011
Duration: 00:00:04.62, start: 0.000000, bitrate: N/A
Stream #0.0: Video: flv, yuv420p, 640x480, 1k tbr, 1k tbn, 1k tbc
Stream #0.1: Audio: nellymoser, 44100 Hz, mono, s16
[buffer @ 0x11ddc950] w:640 h:480 pixfmt:yuv420p
[scale @ 0x11dda610] w:640 h:480 fmt:yuv420p -> w:400 h:300 fmt:yuv420p flags:0xa0000004
[mpeg @ 0x11dd6bd0] VBV buffer size not set, muxing may fail
Output #0, mpeg, to 'user_scaled.mpg':
Metadata:
duration : 5
videocodecid : 2
audiocodecid : 6
canSeekToEnd : true
createdby : FMS 4.0
creationdate : Mon Oct 31 11:43:44 2011
encoder : Lavf52.108.0
Stream #0.0: Video: mpeg1video, yuv420p, 400x300, q=2-31, 200 kb/s, 90k tbn, 60 tbc
Stream #0.1: Audio: mp2, 44100 Hz, mono, s16, 64 kb/s
Stream mapping:
Stream #0.0 -> #0.0
Stream #0.1 -> #0.1
Press [q] to stop encoding
frame= 230 fps= 0 q=10.2 size= 366kB time=3.82 bitrate= 785.6kbits/s dup=175 drop=0
frame= 267 fps= 0 q=10.7 Lsize= 412kB time=4.43 bitrate= 761.3kbits/s dup=203 drop=0
video:370kB audio:36kB global headers:0kB muxing overhead 1.568959%
After much gnashing of teeth, I think the problem has nothing to do with ffmpeg, and everything to do with Quicktime.
Quicktime Player (10.1 (501.5)) scales videos to match the size of the window, and has a minimum window size. So regardless of the actual video size, Quicktime will scale it to at least 480 by 360. This is why the info display has size information in the "Format" section (the true size), but also has a "Current Size" section. Changing the window size changes that latter number.
So, scale videos using ffmpeg either with -vf scale or just -s, but don't trust Quicktime Player to show them to you at the correct size. I recommend VLC as a very capable alternative.