ffmpeg: wrong container fps when muxing raw Xvid to avi

[Selur]

I got a small m4v file (Xvid; small.m4v) and I want to mux into an .avi container.

ffmpeg reports it as:

Stream #0:0: Video: mpeg4 (Advanced Simple Profile), yuv420p, 720x576 [SAR 64:45 DAR 16:9], 25 fps, 25 tbr, 1200k tbn, 25 tbc

MediaInfo reports it as:

Video
Count : 205
Count of stream of this kind : 1
Kind of stream : Video
Kind of stream : Video
Stream identifier : 0
Format : MPEG-4 Visual
Commercial name : MPEG-4 Visual
Format profile : Advanced Simple@L5
Format settings : BVOP2
Format settings, BVOP : 2
Format settings, BVOP : 2
Format settings, QPel : No
Format settings, QPel : No
Format settings, GMC : 0
Format settings, GMC : No warppoints
Format settings, Matrix : Default (H.263)
Format settings, Matrix : Default (H.263)
Internet media type : video/MP4V-ES
Codec : MPEG-4V
Codec : MPEG-4 Visual
Codec/Family : MPEG-4V
Codec profile : Advanced Simple@L5
Codec settings : BVOP
Codec settings, Packet bitstream : No
Codec settings, BVOP : Yes
Codec settings, QPel : No
Codec settings, GMC : 0
Codec settings, GMC : No warppoints
Codec settings, Matrix : Default (H.263)
Width : 720
Width : 720 pixels
Height : 576
Height : 576 pixels
Pixel aspect ratio : 1.422
Display aspect ratio : 1.778
Display aspect ratio : 16:9
Frame rate : 25.000
Frame rate : 25.000 fps
Standard : PAL
Resolution : 8
Resolution : 8 bits
Colorimetry : 4:2:0
Color space : YUV
Chroma subsampling : 4:2:0
Bit depth : 8
Bit depth : 8 bits
Scan type : Progressive
Scan type : Progressive
Interlacement : PPF
Interlacement : Progressive
Compression mode : Lossy
Compression mode : Lossy
Writing library : XviD0063
Writing library : XviD 63
Writing library/Name : XviD
Writing library/Version : 63

Problem is when I remux it with:

ffmpeg -y -i "D:\Encoding Output\small.m4v" -vtag xvid -vcodec copy -map 0:0 -f avi "D:\Encoding Output\small.avi"

ffmpeg reports:

Input #0, m4v, from 'D:\Encoding Output\small.m4v':
Duration: N/A, bitrate: N/A
Stream #0:0: Video: mpeg4 (Advanced Simple Profile), yuv420p, 720x576 [SAR 64:45 DAR 16:9], 25 fps, 25 tbr, 1200k tbn, 25 tbc
Output #0, avi, to 'D:\Encoding Output\small.avi':
Metadata:
ISFT : Lavf53.29.100
Stream #0:0: Video: mpeg4 (xvid / 0x64697678), yuv420p, 720x576 [SAR 64:45 DAR 16:9], q=2-31, 25 fps, 50 tbn, 50 tbc
Stream mapping:
Stream #0:0 -> #0:0 (copy)
Press [q] to stop, [?] for help
frame= 664 fps= 0 q=-1.0 Lsize= 2195kB time=00:00:26.54 bitrate= 677.5kbits/s
video:2158kB audio:0kB global headers:0kB muxing overhead 1.718484%

and the resulting container fps flag is set to 50fps, not 25 fps;
even when I use:

ffmpeg -y -r 25 -i "D:\Encoding Output\small.m4v" -vtag xvid -vcodec copy -map 0:0 -r 25 -f avi "D:\Encoding Output\small.avi"

I still end up with 50fps in the container,... :/

Is this a bug in ffmpeg or am I doing it wrong?

Cu Selur

Ps.: I'm using ffmpeg version N-36635-gceb0dd9.