using janus-pp-rec to generate mp4 file, but h264 profile is not correct

[yangpeiyong]

I have video call encoded in h264 baseline, using janus to record the video into a mjr file.

Then I using janus-pp-rec to convert mjr file to a playable mp4 file.

When I play the mp4 file, the video has many green blocks. And the log of janus-pp-rec has something strange:

[libx264 @ 0x7fe89b001800] using cpu capabilities: MMX2 SSE2Fast SSSE3 SSE4.2 AVX FMA3 BMI2 AVX2 [libx264 @ 0x7fe89b001800] profile High, level 1.3 [libx264 @ 0x7fe89b001800] 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=7 lookahead_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=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

The video send is h264 baseline, why the log shows h264 profile high. And the video play is not corrent.

I try to use ffmpeg to change mp4 file from profile high to profile baseline, the green blocks disappears.

[lminiero]

janus-pp-rec doesn't transcode, it only copies packets. IIRC we check what profile is in the first sps/pps we get and set that in the mp4 header, but I may be wrong. In case, that's what the RTP packets tell us and so that's what we save. Anyway, not at the office until tomorrow so can't check now.

[lminiero]

IIRC we check what profile is in the first sps/pps we get and set that in the mp4 header, but I may be wrong

I was indeed wrong: we do read the profile in janus_pp_h264_parse_sps, but we ignore it (we only use that to extract width and height). I guess that we can just extract the profile that way too, and save it to the header, since I guess by default this falls back to 100 (high).

@yangpeiyong do you have an .mjr we can use to test a fix, when available?

[lminiero]

Mh, just tried with two different .mjr files (one baseline, one high), and both were converted to playable .mp4 files: mediainfo seems to recognize the right profile for both. If you can share the .mjr file I asked about, I'll have a look to see why it's not working in that case.

[yangpeiyong]

Mh, just tried with two different .mjr files (one baseline, one high), and both were converted to playable .mp4 files: mediainfo seems to recognize the right profile for both. If you can share the .mjr file I asked about, I'll have a look to see why it's not working in that case.

Yes, I can send you .mjr file. Can you give me you email adress?

[lminiero]

You can send it at [redacted].

[lminiero]

@yangpeiyong please let me know when you've sent the mail, as I'd rather not keep the mail address here (I'm pretty sure we'll start getting spam now :wink: )

[yangpeiyong]

@yangpeiyong please let me know when you've sent the mail, as I'd rather not keep the mail address here (I'm pretty sure we'll start getting spam now 😉 )

Hi, Iminiero, I have just sent the mail.

[lminiero]

I think the recording is broken, this is what is printed when we use the --parse option:

SSRC detected: 271031110
[WARN] Dropping packet with unexpected SSRC: 1457645387 != 271031110
[WARN] Dropping packet with unexpected SSRC: 1457645387 != 271031110
[WARN] Dropping packet with unexpected SSRC: 1457645387 != 271031110
[WARN] Dropping packet with unexpected SSRC: 1457645387 != 271031110
[WARN] Dropping packet with unexpected SSRC: 1457645387 != 271031110
[WARN] Dropping packet with unexpected SSRC: 1457645387 != 271031110
[WARN] Dropping packet with unexpected SSRC: 1457645387 != 271031110
Counted 2508 RTP packets
Counted 2501 frame packets
[WARN] Profile is not baseline (-55 != 66)
  -- 240x240 (fps [2250,104940] ~ 40)

There are two SSRCs in it for some reason, which is weird: are you recording from your own plugin?

Besides, it finds a profile that doesn't exist (-55) when evaluating what it believes to be an SPS/PPS packet: this might mean that the recording is not actually H.264. The resolution is weird as well (square?) but that may be intended.

[lminiero]

Processing the recording actually crashed the processor for me, due to a buffer overflow that is now fixed in https://github.com/meetecho/janus-gateway/commit/60e5fef96548a0ada1f8bffd33b840eab4b5ad5f

Now I get an mp4 file that I can play: I do see some artifacts (ghosting, mostly), but no green blocks. Inspecting the file with mediainfo the profile seems correct:

Format                                   : AVC
Format/Info                              : Advanced Video Codec
Format profile                           : Baseline@L2.1

and same thing with FFprobe:

    Stream #0:0(und): Video: h264 (Constrained Baseline) (avc1 / 0x31637661), yuv420p, 240x240, 62 kb/s, 19.69 fps, 30 tbr, 90k tbn, 180k tbc (default)

As such, I think the tool is doing its job, and what you experienced may have been a side effect of the crash I was getting instead. Closing as I don't think there's an issue, but feel free to reopen if you can provide more details: if you can provide a fix to pp-h264.c that works for you as a pull request, I'll gladly review that too.