[rtmpdump] Discrepancies Between Dumped Video And Source Video

[Howard Chu]

Nickolaus Padgett wrote:
> On Wed, Jul 21, 2010 at 3:00 PM, Howard Chu<hyc at highlandsun.com>  wrote:
>>> 2) The source video is 74.1 MB on disk (74,139,578 bytes), however,
>>> the RTMPdump video is 36.5 MB on disk (36,457,236 bytes).  Why is
>>> this?  Are there elementary streams in the source video that are not
>>> being transfered from the RTMP server?
>>
>> The metadata in your log certainly implies that there are two video and two
>> audio streams.
>
> I looked at the original source file and there are only two streams;
> one audio and one video.  What other reasons would explain the drastic
> difference in file size?  You can download the original source video
> from http://static.playonsports.com.s3.amazonaws.com/example_expected.mp4.

You are quite mistaken. There are 6 streams in that file.

ffprobe example_expected.mp4
FFprobe version SVN-r24034, Copyright (c) 2007-2010 the FFmpeg developers
   built on Jul  6 2010 11:27:54 with gcc 4.4.3
   configuration: --enable-librtmp --extra-libs='-lrtmp -lssl -lcrypto' 
--enable-libx264 --enable-libfaac --enable-gpl --enable-nonfree 
--enable-pthreads --enable-libxvid --enable-libmp3lame --disable-encoder=aac
   libavutil     50.20. 0 / 50.20. 0
   libavcodec    52.79. 1 / 52.79. 1
   libavformat   52.73. 0 / 52.73. 0
   libavdevice   52. 2. 0 / 52. 2. 0
   libavfilter    1.20. 1 /  1.20. 1
   libswscale     0.11. 0 /  0.11. 0
[mov,mp4,m4a,3gp,3g2,mj2 @ 0x1d230a0] Could not find codec parameters (Data: 
rtp  / 0x20707472, 67 kb/s)
[mov,mp4,m4a,3gp,3g2,mj2 @ 0x1d230a0] Could not find codec parameters (Data: 
rtp  / 0x20707472, 440 kb/s)
[mov,mp4,m4a,3gp,3g2,mj2 @ 0x1d230a0] Could not find codec parameters (Data: 
mp4s / 0x7334706D, 0 kb/s)
     Last message repeated 1 times
Input #0, mov,mp4,m4a,3gp,3g2,mj2, from 'example_expected.mp4':
   Metadata:
     major_brand     : mp42
     minor_version   : 1
     compatible_brands: isommp41avc1
   Duration: 00:09:59.39, start: 0.000000, bitrate: 128 kb/s
     Stream #0.0(eng): Data: rtp  / 0x20707472, 67 kb/s
     Stream #0.1(eng): Data: rtp  / 0x20707472, 440 kb/s
     Stream #0.2(eng): Video: h264, yuv420p, 480x360 [PAR 1:1 DAR 4:3], 411 
kb/s, 29.97 fps, 29.97 tbr, 2997 tbn, 59.94 tbc
     Stream #0.3(eng): Audio: aac, 44100 Hz, stereo, s16, 64 kb/s
     Stream #0.4(eng): Data: mp4s / 0x7334706D, 0 kb/s
     Stream #0.5(eng): Data: mp4s / 0x7334706D, 0 kb/s


>   You can download the RTMPdump video from
> http://static.playonsports.com.s3.amazonaws.com/example_actual.mp4.flv.
>
>>> 3) The RTMPdump video is not seekable, however, the source video is
>>> seekable.
>>
>> Sounds like your player is broken. FLVs should always be seekable.
>
> I used VLC 1.0.5 to play the video.  Try the actual link above and
> seek to 75% into the video.

I tried a bunch of different players (mplayer, ffplay, totem), they all 
behaved the same with both files. Seeking worked up to about 50% (4:30) into 
the file. There's nothing to indicate that rtmpdump is involved in any of the 
behavior you're seeing. Go talk to whoever provided the video data.