我有一个包含数千个flv文件的库，我需要将其转换为mp4。我试图使用ffmpeg这样做，但我遇到了一些问题。
主要：
1）我无法在不重新编码的情况下从FLV切换到MP4。如果我这样做，我会收到来自ffmpeg的消息＆＃34;无法在流＃0中找到编解码器flv1的标签，当前容器中不支持编解码器＆＃34;
2）如果我重新编码视频，结果视频质量较低（我看到VLC中的伪像）和更大。例如，一个视频从2.5MB变为4.3MB（几乎是大小的两倍）
鉴于第二，你可能会问自己 - 为什么转换呢？
答案是我需要将这些流式传输到移动设备（手机/平板电脑等），并且不支持flv。所以我需要转换文件，但我不能容忍超过最小的质量变化，最好是零到不增加大小。
这是我正在运行的ffmpeg命令：
ffmpeg -i $_.FullName -movflags faststart -profile:v baseline -level 3.0 "$($_.BaseName).mp4"
（请注意，我从powershell运行ffmpeg所以：
$_.FullName = the original file name
"$($_.BaseName).mp4" = the original file name with mp4 extension)
任何FFMPEG大师都可以帮助我理解我做错了什么吗？是否有一些参数我可以使用这些参数来减少质量和类似尺寸？
注意我还试过＆＃34; -c：v libx264 -preset veryslow -crf 23 -c：副本＆＃34;。使用礼物＆＃34; veryslow＆＃34;没有任何明显的差异。
更新 我使用以下选项：
ffmpeg -i $_.FullName -c:v libx264 -preset veryslow -crf 19 -c:a copy "$($_.BaseName).mp4"
这里有完整的输出：
ffmpeg version 2.8.4 Copyright (c) 2000-2015 the FFmpeg developers
built with gcc 5.2.0 (GCC)
configuration: --enable-gpl --enable-version3 --disable-w32threads --enable-avisynth --enable-bzlib --enable-fontconfi
g --enable-frei0r --enable-gnutls --enable-iconv --enable-libass --enable-libbluray --enable-libbs2b --enable-libcaca --
enable-libdcadec --enable-libfreetype --enable-libgme --enable-libgsm --enable-libilbc --enable-libmodplug --enable-libm
p3lame --enable-libopencore-amrnb --enable-libopencore-amrwb --enable-libopenjpeg --enable-libopus --enable-librtmp --en
able-libschroedinger --enable-libsoxr --enable-libspeex --enable-libtheora --enable-libtwolame --enable-libvidstab --ena
ble-libvo-aacenc --enable-libvo-amrwbenc --enable-libvorbis --enable-libvpx --enable-libwavpack --enable-libwebp --enabl
e-libx264 --enable-libx265 --enable-libxavs --enable-libxvid --enable-lzma --enable-decklink --enable-zlib
libavutil 54. 31.100 / 54. 31.100
libavcodec 56. 60.100 / 56. 60.100
libavformat 56. 40.101 / 56. 40.101
libavdevice 56. 4.100 / 56. 4.100
libavfilter 5. 40.101 / 5. 40.101
libswscale 3. 1.101 / 3. 1.101
libswresample 1. 2.101 / 1. 2.101
libpostproc 53. 3.100 / 53. 3.100
Input #0, flv, from 'C:\Users\brad\Desktop\ffmpeg\Originals\1019800-1278575542468.flv':
Metadata:
canSeekToEnd : false
createdby : FMS 3.5
creationdate : Thu Jul 08 03:52:25 2010
Duration: 00:00:56.94, start: 0.000000, bitrate: 360 kb/s
Stream #0:0: Video: flv1, yuv420p, 320x240, 1k tbr, 1k tbn, 1k tbc
[libx264 @ 02cf7300] using cpu capabilities: MMX2 SSE2Fast SSSE3 SSE4.2
[libx264 @ 02cf7300] profile High, level 4.2
[libx264 @ 02cf7300] 264 - core 148 r2638 7599210 - H.264/MPEG-4 AVC codec - Copyleft 2003-2015 - http://www.videolan.or
g/x264.html - options: cabac=1 ref=16 deblock=1:0:0 analyse=0x3:0x133 me=umh subme=10 psy=1 psy_rd=1.00:0.00 mixed_ref=1
me_range=24 chroma_me=1 trellis=2 8x8dct=1 cqm=0 deadzone=21,11 fast_pskip=1 chroma_qp_offset=-2 threads=7 lookahead_th
reads=1 sliced_threads=0 nr=0 decimate=1 interlaced=0 bluray_compat=0 constrained_intra=0 bframes=8 b_pyramid=2 b_adapt=
2 b_bias=0 direct=3 weightb=1 open_gop=0 weightp=2 keyint=250 keyint_min=25 scenecut=40 intra_refresh=0 rc_lookahead=60
rc=crf mbtree=1 crf=19.0 qcomp=0.60 qpmin=0 qpmax=69 qpstep=4 ip_ratio=1.40 aq=1:1.00
Output #0, mp4, to '1019800-1278575542468.mp4':
Metadata:
canSeekToEnd : false
createdby : FMS 3.5
creationdate : Thu Jul 08 03:52:25 2010
encoder : Lavf56.40.101
Stream #0:0: Video: h264 (libx264) ([33][0][0][0] / 0x0021), yuv420p, 320x240, q=-1--1, 1k fps, 16k tbn, 1k tbc
Metadata:
encoder : Lavc56.60.100 libx264
Stream mapping:
Stream #0:0 -> #0:0 (flv1 (flv) -> h264 (libx264))
Press [q] to stop, [?] for help
frame=57117 fps=199 q=-1.0 Lsize= 5611kB time=00:00:57.11 bitrate= 804.8kbits/s dup=56685 drop=0
video:5184kB audio:0kB subtitle:0kB other streams:0kB global headers:0kB muxing overhead: 8.229259%
[libx264 @ 02cf7300] frame I:230 Avg QP:15.92 size: 8828
[libx264 @ 02cf7300] frame P:6399 Avg QP:17.19 size: 385
[libx264 @ 02cf7300] frame B:50488 Avg QP:27.13 size: 16
[libx264 @ 02cf7300] consecutive B-frames: 0.4% 0.0% 0.0% 0.0% 0.0% 2.3% 0.0% 0.0% 97.2%
[libx264 @ 02cf7300] mb I I16..4: 2.9% 92.6% 4.5%
[libx264 @ 02cf7300] mb P I16..4: 0.1% 2.0% 0.2% P16..4: 2.4% 1.2% 1.1% 0.1% 0.0% skip:92.9%
[libx264 @ 02cf7300] mb B I16..4: 0.0% 0.0% 0.0% B16..8: 2.6% 0.0% 0.0% direct: 0.0% skip:97.3% L0:45.0% L1:5
4.9% BI: 0.0%
[libx264 @ 02cf7300] 8x8 transform intra:90.7% inter:76.5%
[libx264 @ 02cf7300] direct mvs spatial:75.2% temporal:24.8%
[libx264 @ 02cf7300] coded y,uvDC,uvAC intra: 94.4% 96.8% 64.8% inter: 0.3% 0.4% 0.1%
[libx264 @ 02cf7300] i16 v,h,dc,p: 16% 25% 18% 41%
[libx264 @ 02cf7300] i8 v,h,dc,ddl,ddr,vr,hd,vl,hu: 19% 28% 30% 4% 3% 3% 4% 4% 5%
[libx264 @ 02cf7300] i4 v,h,dc,ddl,ddr,vr,hd,vl,hu: 18% 22% 9% 11% 8% 7% 10% 8% 7%
[libx264 @ 02cf7300] i8c dc,h,v,p: 30% 34% 23% 13%
[libx264 @ 02cf7300] Weighted P-Frames: Y:0.1% UV:0.1%
[libx264 @ 02cf7300] ref P L0: 74.1% 19.7% 4.5% 0.6% 0.1% 0.2% 0.0% 0.1% 0.0% 0.1% 0.0% 0.2% 0.0% 0.2% 0.0%
0.1%
[libx264 @ 02cf7300] ref B L0: 95.5% 1.6% 0.7% 0.5% 0.4% 0.3% 0.3% 0.2% 0.1% 0.1% 0.1% 0.1% 0.1% 0.0% 0.0%
[libx264 @ 02cf7300] ref B L1: 84.5% 15.5%
[libx264 @ 02cf7300] kb/s:743.46
Original Video Size: 2.44 MB
New Video Size: 5.6 MB