title: Add SRT subtitle to video with ffmpeg
body: <p>I use ffmpeg to encode, and add subtitle to a video by following command</p>
  <pre><code>$ ffmpeg -i hifi.avi -i hifi.srt -acodec libfaac -ar 48000 -ab 128k -ac 2 -vcodec libx264 -vpre ipod640 -s 480x240 -b 256k -scodec copy  hifi.m4v -newsubtitle
  </code></pre>
  <p>Here is the output</p>
  <pre><code>ffmpeg version 0.8.git, Copyright (c) 2000-2011 the FFmpeg developers
    built on Aug  4 2011 11:11:39 with gcc 4.5.2
    configuration: --extra-cflags=-I/usr/local/include --extra-ldflags=-L/usr/local/lib --disable-shared --enable-static --enable-gpl --enable-postproc --enable-pthreads --enable-ffplay --disable-ffserver --enable-memalign-hack --enable-nonfree --enable-libfaac --arch=x86 --enable-swscale --enable-libx264 --enable-avfilter --enable-debug=3
    libavutil    51. 11. 1 / 51. 11. 1
    libavcodec   53.  9. 1 / 53.  9. 1
    libavformat  53.  6. 0 / 53.  6. 0
    libavdevice  53.  2. 0 / 53.  2. 0
    libavfilter   2. 27. 5 /  2. 27. 5
    libswscale    2.  0. 0 /  2.  0. 0
    libpostproc  51.  2. 0 / 51.  2. 0
  Input #0, avi, from 'hifi.avi':
    Metadata:
      encoder         : VirtualDubMod 1.5.4.1 (build 2178/release)
      IAS1            : English
    Duration: 01:49:02.20, start: 0.000000, bitrate: 897 kb/s
      Stream #0.0: Video: mpeg4 (Simple Profile), yuv420p, 544x304 [SAR 1:1 DAR 34:19], 25 tbr, 25 tbn, 25 tbc
      Stream #0.1: Audio: mp3, 48000 Hz, stereo, s16, 32 kb/s
  [srt @ 0152c100] Estimating duration from bitrate, this may be inaccurate
  Input #1, srt, from 'hifi.srt':
    Duration: N/A, start: 56.080000, bitrate: N/A
      Stream #1.0: Subtitle: srt
  File 'hifi.m4v' already exists. Overwrite ? [y/N] y
  [buffer @ 02548920] w:544 h:304 pixfmt:yuv420p tb:1/1000000 sar:1/1 sws_param:
  [scale @ 02558ee0] w:544 h:304 fmt:yuv420p -&gt; w:480 h:240 fmt:yuv420p flags:0x4
  [libx264 @ 02547f20] Default settings detected, using medium profile
  [libx264 @ 02547f20] using SAR=1/1
  [libx264 @ 02547f20] using cpu capabilities: MMX2 SSE2Fast SSSE3 FastShuffle SSE4.1 Cache64
  [libx264 @ 02547f20] profile High, level 3.0
  [libx264 @ 02547f20] 264 - core 115 - 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=0x3:0x113 me=hex subme=7 psy=1 psy_rd=1.00:0.00 mixed_ref=1 me_range=16 chroma_me=1 trellis=1 8x8dct=1 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=2 b_adapt=1 b_bias=0 direct=1 weightb=1 open_gop=0 weightp=0 keyint=250 keyint_min=25 scenecut=40 intra_refresh=0 rc_lookahead=40 rc=abr mbtree=1 bitrate=256 ratetol=1.0 qcomp=0.60 qpmin=0 qpmax=69 qpstep=4 vbv_maxrate=10000 vbv_bufsize=10000 nal_hrd=none ip_ratio=1.40 aq=1:1.00
  Output #0, ipod, to 'hifi.m4v':
      Stream #0.0: Video: libx264, yuv420p, 480x240 [SAR 1:1 DAR 2:1], q=2-31, 256 kb/s, 90k tbn, 25 tbc
      Stream #0.1: Audio: libfaac, 48000 Hz, 2 channels, s16, 128 kb/s
      Stream #0.2: Subtitle: srt
      Stream #0.3: Subtitle: [0][0][0][0] / 0x0000, 64 kb/s
  Stream mapping:
    Stream #0.0 -&gt; #0.0
    Stream #0.1 -&gt; #0.1
    Stream #1.0 -&gt; #0.2
    Stream #1.0 -&gt; #0.3
  Encoder (codec id 0) not found for output stream #0.3
  </code></pre>
  <p>Can anyone tell what is wrong with my command?</p>