[FFmpeg-user] Unsophisticated user has a question

[ffmpeg@riventree.com]

Hello all,

I've encountered something that makes me suspicious that I've lost data. I
have a .MOD file (Grrr Cannon vidcams) that takes up 39M of storage. I
converted it to .mp4 with the simplest possible command:

jde-desktop% ffmpeg -i 002.MOD 002.mp4

And the resultant .mp4 is 9.9M!

A cursory (and uninformed) glance at the output shows a [720x480 / yuv420p
/ 29.97fps] stream in and the same thing out. The video input is
"mpeg2video" and the output is "libx264", the audio is AC3 in and AAC out.

*I need to know if that's just better packing or (this is the problem) I've
lost data in the conversion.*

How can I find out?

Below is the complete output from ffmpeg. Can anyone explain the 4x size
difference with the data there?

-Jeff

ffmpeg version 0.8.6-4:0.8.6-0ubuntu0.12.04.1, Copyright (c) 2000-2013 the
Libav developers
  built on Apr  2 2013 17:02:36 with gcc 4.6.3
*** THIS PROGRAM IS DEPRECATED ***
This program is only provided for compatibility and will be removed in a
future release. Please use avconv instead.
[mpeg @ 0x12699a0] max_analyze_duration reached
Input #0, mpeg, from '002.MOD':
  Duration: 00:00:05.97, start: 0.220756, bitrate: 5272 kb/s
    Stream #0.0[0x1e0]: Video: mpeg2video (Main), yuv420p, 720x480 [PAR
32:27 DAR 16:9], 9600 kb/s, 29.97 fps, 29.97 tbr, 90k tbn, 59.94 tbc
    Stream #0.1[0x80]: Audio: ac3, 48000 Hz, stereo, s16, 256 kb/s
[buffer @ 0x1271f60] w:720 h:480 pixfmt:yuv420p
[libx264 @ 0x1271220] using SAR=32/27
[libx264 @ 0x1271220] using cpu capabilities: MMX2 SSE2Fast SSSE3 Cache64
[libx264 @ 0x1271220] profile Main, level 3.0
[libx264 @ 0x1271220] 264 - core 120 r2151 a3f4407 - H.264/MPEG-4 AVC codec
- Copyleft 2003-2011 - http://www.videolan.org/x264.html - options: cabac=1
ref=3 deblock=1:0:0 analyse=0x1:0x111 me=hex subme=7 psy=1 psy_rd=1.00:0.00
mixed_ref=0 me_range=16 chroma_me=1 trellis=1 8x8dct=0 cqm=0 deadzone=21,11
fast_pskip=1 chroma_qp_offset=-2 threads=1 sliced_threads=0 nr=0 decimate=1
interlaced=0 bluray_compat=0 constrained_intra=0 bframes=3 b_pyramid=0
b_adapt=1 b_bias=0 direct=1 weightb=0 open_gop=1 weightp=2 keyint=250
keyint_min=25 scenecut=40 intra_refresh=0 rc_lookahead=40 rc=crf mbtree=1
crf=23.0 qcomp=0.60 qpmin=0 qpmax=69 qpstep=4 ip_ratio=1.25 aq=1:1.00
Output #0, mp4, to '002.mp4':
  Metadata:
    encoder         : Lavf53.21.1
    Stream #0.0: Video: libx264, yuv420p, 720x480 [PAR 32:27 DAR 16:9],
q=-1--1, 30k tbn, 29.97 tbc
    Stream #0.1: Audio: libvo_aacenc, 48000 Hz, stereo, s16, 200 kb/s
Stream mapping:
  Stream #0.0 -> #0.0
  Stream #0.1 -> #0.1
Press ctrl-c to stop encoding
[mpeg2video @ 0x126ba40] warning: first frame is no keyframe
    Last message repeated 1 times    734kB time=4.30 bitrate=1396.2kbits/s

frame=  180 fps= 29 q=29.0 Lsize=     969kB time=5.97 bitrate=1328.6kbits/s

video:816kB audio:147kB global headers:0kB muxing overhead 0.607864%
frame I:1     Avg QP:24.04  size: 59660
[libx264 @ 0x1271220] frame P:66    Avg QP:23.79  size: 10898
[libx264 @ 0x1271220] frame B:113   Avg QP:28.92  size:   494
[libx264 @ 0x1271220] consecutive B-frames:  3.3% 17.8% 63.3% 15.6%
[libx264 @ 0x1271220] mb I  I16..4:  5.9%  0.0% 94.1%
[libx264 @ 0x1271220] mb P  I16..4:  0.0%  0.0%  0.1%  P16..4: 62.1% 11.2%
11.3%  0.0%  0.0%    skip:15.4%
[libx264 @ 0x1271220] mb B  I16..4:  0.0%  0.0%  0.0%  B16..8: 34.0%  0.6%
 0.1%  direct: 0.3%  skip:64.9%  L0:30.8% L1:59.4% BI: 9.8%
[libx264 @ 0x1271220] coded y,uvDC,uvAC intra: 93.2% 91.8% 54.2% inter:
14.9% 16.3% 1.1%
[libx264 @ 0x1271220] i16 v,h,dc,p: 26% 17% 15% 42%
[libx264 @ 0x1271220] i4 v,h,dc,ddl,ddr,vr,hd,vl,hu: 25% 14% 12%  6%  8%
10%  7% 10%  7%
[libx264 @ 0x1271220] i8c dc,h,v,p: 44% 17% 31%  9%
[libx264 @ 0x1271220] Weighted P-Frames: Y:0.0% UV:0.0%
[libx264 @ 0x1271220] ref P L0: 63.4%  8.1% 16.6% 11.9%
[libx264 @ 0x1271220] ref B L0: 85.8% 14.2%
[libx264 @ 0x1271220] kb/s:1111.83
jde-desktop%