[FFmpeg-user] -s[:stream_specifier] size (input/output, per-stream)

[jd1008]

On 03/24/2016 07:37 PM, Moritz Barsnick wrote:
> On Thu, Mar 24, 2016 at 17:50:40 -0600, jd1008 wrote:
>
>> Reason I am transcoding into mpeg1 is because the apps that create the
>> DVD format for playback on regular DVD's
>> take them way freaking too long to do the transcoding to mpeg1 (and that
>> is what they do to every video I try to
>> convert to DVD using the dvd creation apps.
>> ffmpeg seems to do it a lot faster.
>> So, when is ue these apps and the input video is already in mpeg1
>> format, they just proceed to create the
>> DVD format without transcoding.
> I understand, I used to use similar programs, and appreciated that they
> took my ffmpeg created input without reencoding.
>
> But: mpeg2video is a much more effective codec for DVD. ffmpeg even has
> a shortcut-option "-target dvd" (or "-target pal-dvd", "-target
> ntsc-dvd") which sets several encoding options for DVD compatibility.
>
> Moritz
Here is something strange or interesting when I add  -target ntsc-dvd
ffmpeg -i a_short video.mp4 -s 1920x1080 -c:v mpeg1video -q:v 1 -mbd rd 
-target ntsc-dvd -y a_short_video.mpg
Playing back the mpg video with ffplay yielded this output:

Input #0, mpeg, from 
'I.Am.Number.Four.2011.1080p.BluRay.H264.AAC-RARBG-2.mpg':
   Duration: 00:17:28.32, start: 0.528033, bitrate: 3355 kb/s
     Stream #0:0[0x1bf]: Data: dvd_nav_packet
     Stream #0:1[0x1e0]: Video: *mpeg2video* (Main), yuv420p(tv), 
*720x480* [SAR 32:27 DAR 16:9], max. 9000 kb/s, 29.97 fps, 29.97 tbr, 
90k tbn, 59.94 tbc
     Stream #0:2[0x80]: Audio: ac3, 48000 Hz, 5.1(side), fltp, 448 kb/s

And notice, ffplay says that the format is mpeg2 instead of mpeg1.
Is -target option reducing the resolution and changing the format?