[FFmpeg-devel] Redirecting MP4 muxed data to socket using movflags resets timestamp

[Parth Shah]

I am using FFMPEG library to mux H.264 and AAC frames to MP4 file. I do 
that C program.
I store H.264 and AAC frame's timestamp in epoch format.

I use ffprobe to check timestamps that stored in the MP4 file, ffprobe 
confirms that file is in MP4 format and timestamps are stored correctly. 
below is the output of ffprobe.

  * ffprobe -show_packets 20140805095931.mp4

Input #0, mov,mp4,m4a,3gp,3g2,mj2, from '20140805095931.mp4':
Metadata:
major_brand     : isom
minor_version   : 512
compatible_brands: isomiso2avc1mp41
encoder         : Lavf54.29.104
Duration: 00:01:39.70, start: 1407232771.984000, bitrate: 1063 kb/s
Stream #0.0(und): Video: h264 (High), yuv420p, 960x540, 999 kb/s, 30 
fps, 59.94 tbr, 1k tbn, 60 tbc
Stream #0.1(und): Audio: aac, 48000 Hz, mono, s16, 53 kb/s
[PACKET]
codec_type=video
stream_index=0
pts=1407232771984
pts_time=1407232771.984000
dts=1407232771984
dts_time=1407232771.984000
duration=34
duration_time=0.034000
size=24556.000000
pos=48
flags=K
[/PACKET]
[PACKET]
codec_type=video
stream_index=0
pts=1407232772018
pts_time=1407232772.018000
dts=1407232772018
dts_time=1407232772.018000
duration=33
duration_time=0.033000
size=3180.000000
pos=24604
flags=_
[/PACKET]
[PACKET]
codec_type=video
stream_index=0
pts=1407232772051
pts_time=1407232772.051000
dts=1407232772051
dts_time=1407232772.051000
duration=33
duration_time=0.033000
size=3209.000000
pos=27784
flags=_
[/PACKET]


My goal is reading this muxed MP4 data from MP4 file and send this muxed 
mp4 data to the client over socket without creating any temporary file. 
My actual goal is to write a C program though.

I tried using protocols tcp and udp but they are not working with Mp4 
format and gives error as below.
*
**ffmpeg -i 20140805095931.mp4 -f mp4 -vcodec copy tcp://10.99.19.163:8888**
**
**[mp4 @ 0xb1e1920] muxer does not support non seekable output **
**Could not write header for output file #0 (incorrect codec parameters 
?): Invalid argument*

So, I read somewhere about moov atom and tried it with following command

*ffmpeg -i 20140805095931.mp4 -movflags isml+frag_keyframe -f mp4 
-vcodec copy tcp://10.99.19.163:8888*

using above commandline I am able to send mp4 file to the client using 
tcp protocol that ffmpeg supports.

But when I apply ffprobe on the generated MP4 file timestamp resets to 0 
, even starttime becomes 0.0000. Below is the output of ffmpeg.

  *   ffprobe -show_packets out.mp4


Input #0, mov,mp4,m4a,3gp,3g2,mj2, from 'out.mp4':
Metadata:
major_brand     : isom
minor_version   : 512
compatible_brands: isomiso2avc1mp41
encoder         : Lavf55.48.100
Duration: 00:01:39.71, start: 0.000000, bitrate: 1059 kb/s
Stream #0:0(und): Video: h264 (High) (avc1 / 0x31637661), yuv420p, 
960x540, 999 kb/s, 30 fps, 30 tbr, 16k tbn, 60 tbc (default)
Metadata:
handler_name    : VideoHandler
Stream #0:1(und): Audio: aac (mp4a / 0x6134706D), 48000 Hz, mono, fltp, 
53 kb/s (default)
Metadata:
handler_name    : SoundHandler
[PACKET]
codec_type=video
stream_index=0
pts=0
pts_time=0.000000
dts=0
dts_time=0.000000
duration=533
duration_time=0.033313
convergence_duration=N/A
convergence_duration_time=N/A
size=24556
pos=3853
flags=K
[/PACKET]
[PACKET]
codec_type=video
stream_index=0
pts=544
pts_time=0.034000
dts=544
dts_time=0.034000
duration=533
duration_time=0.033313
convergence_duration=N/A
convergence_duration_time=N/A
size=3180
pos=28409
flags=_
[/PACKET]
[PACKET]
codec_type=video
stream_index=0
pts=1072
pts_time=0.067000
dts=1072
dts_time=0.067000
duration=533
duration_time=0.033313
convergence_duration=N/A
convergence_duration_time=N/A
size=3209
pos=31589
flags=_
[/PACKET]

My question is why this timestamps gets changed? Is thereant method to 
send MP4 file over socket without changing its timestamp?


Any help or advice? Thank you in advance.