[1.x] 1.0.1 janus-pp-rec convert to mp4

[barakpp]

What version of Janus is this happening on?
1.0.1

Have you tested a more recent version of Janus too?
No.

Was this working before?
I did not check it in earlier versions

Is there a gdb or libasan trace of the issue?
No

Additional context
Hi guys,

I have some issue with janus-pp-rec.
I record RTP stream which encoded with h264 codec using janus videoroom plugin. It successfully create MJR file.

When I try to use janus-pp-rec to convert this MJR file to MP4 file I get MP4 which missing some information.
I tried to create a thumbnail from this mp4 but get an error (fluent-ffmpeg using streams), I also used online MP4 analyzer to check the file and it cannot be parsed.

Janus command:
janus-pp-rec input.mjr janus.mp4 - also tried with --format flag.

ffmpeg thumbnail command:
ffmpeg -ss 00:00:01 -i pipe:0 -y -an -vframes 1 -filter:v scale=w=320:h=240 out.png

But when I re create the mp4 without encoding using this command:
ffmpeg -i .\janus.mp4 -c copy -f mp4 out.mp4

the online analyzer works and also the ffmpeg command for creating thumbnail works.

• After some checks it seems that MP4 analyzer expects to get as a first frame I-Frame and the MP4 which generated by janus-pp-rec starts with P-frame.
• I compared two MP4 files, one which works with the ffmpeg command of thumbnail creation and janus's MP4.
  and it seems their have different structure:

1. The MP4 which works has this structure:
   

2. Janus's MP4 has this structure:
   

So I think because I work with pipe ffmpeg cant find the relevant data on the media because the moov part appended after mdat part so I try to use --faststart flag in janus-pp-rec command and got an error.
Janus version: 1001 (1.0.1)
Janus commit: 86cce9f
Compiled on: Wed May 25 08:56:45 UTC 2022

Logging level: 4

Source file: 2022-08-15T18-53-34.322Z-video-0.mjr
Target file: s2.mp4

File is 7677916 bytes
Pre-parsing file to generate ordered index...
This is a video recording:
-- Codec: h264
-- Created: 1660589614342303
-- Written: 1660589615182310
SSRC detected: 3564857702
Counted 6658 RTP packets
Counted 6658 frame packets
-- 1280x720 (fps [2970,11880] ~ 30)
[libx264 @ 0x5586eecdc640] using cpu capabilities: MMX2 SSE2Fast SSSE3 SSE4.2 AVX FMA3 BMI2 AVX2
[libx264 @ 0x5586eecdc640] profile High, level 3.1, 4:2:0, 8-bit
[libx264 @ 0x5586eecdc640] 264 - core 160 r3011 cde9a93 - H.264/MPEG-4 AVC codec - Copyleft 2003-2020 - 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=22 lookahead_threads=3 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=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=1.40 aq=1:1.00
First keyframe: 56430
[mp4 @ 0x5586eecd9380] Starting second pass: moving the moov atom to the beginning of the file
[mp4 @ 0x5586eecd9380] Unable to re-open output file for the second pass (faststart)
s2.mp4 is 7521227 bytes
Bye!

link to MP4 analyzer: https://lulebo.github.io/

I attach the files so I will be glad if you can try to understand what is the problem in the conversion process.
Thank you very much

janus.mp4

out.mp4

[barakpp]

2022-08-11T11-47-08.569Z-video-0.zip

[atoppi]

It is not clear to me how you are using pipes with ffmpeg and if that plays a role in your issue.

I've done a quick test with the following specs:

• latest janus master
• latest Chrome/Linux published in a h264 (profile 42e01f) room

Then started the mjr recording with a configure request and closed the session after a while.

Converted input.mjr to janus.mp4

atoppi@atoppi:/tmp/recordings$ janus-pp-rec input.mjr janus.mp4
Janus version: 1100 (1.1.0)
Janus commit: 4346c1ad387fa0a710a45d978ee980d83a756caa
Compiled on:  lun 22 ago 2022, 10:34:24, CEST

Logging level: 4

Source file: input.mjr
Target file: janus.mp4

File is 10740609 bytes
Pre-parsing file to generate ordered index...
Video orientation extension ID: 13
This is a video recording:
  -- Codec:   h264
  -- Created: 1661158778125644
  -- Written: 1661158778226633
SSRC detected: 1446579215
Counted 9796 RTP packets
Counted 9796 frame packets
[   0.000s] Video rotation: 0 degrees
  -- 640x480 (fps [2340,6210] ~ 38)
[libx264 @ 0x55f268229dc0] using cpu capabilities: MMX2 SSE2Fast SSSE3 SSE4.2 AVX FMA3 BMI2 AVX2
[libx264 @ 0x55f268229dc0] profile High, level 3.1
[libx264 @ 0x55f268229dc0] 264 - core 155 r2917 0a84d98 - H.264/MPEG-4 AVC codec - Copyleft 2003-2018 - 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=12 lookahead_threads=2 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=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=1.40 aq=1:1.00
First keyframe: 0
janus.mp4 is 10458188 bytes
Bye!

I'v got a mp4 file that the online tool you linked was able to parse.

Finally I got a thumbnail with the following command (not using pipes)

ffmpeg -ss 00:00:01 -i janus.mp4 -y -an -vframes 1 -filter:v scale=w=320:h=240 out.png

[lminiero]

The error that's reported is related to faststart:

Unable to re-open output file for the second pass

and I can replicate that one too. Without faststart it does work fine. I'll have a look.

[lminiero]

The above commit seems to fix it for me, please let me know if that's not the case.