Multitrack Audio is not Supported

[ggnull35]

I try below command:

/opt/penc/sbin/bmdcapture --SIGTRAP --trap_nosignal 10 --sub_timeout -1 -m 10 -d 2 --portfile HEVC_RTMP_TEST_MA_port.conf -s 16 -c 2 -C 0 -V 4 -A 2 -p 8 -F nut -o strict=experimental:syncpoints=none -f pipe:1 | /opt/ffmpeg/bin/ffmpeg -ppid /opt/penc/run/HEVC_RTMP_TEST_MA.pid -pikotv_portfile /opt/penc/run/HEVC_RTMP_TEST_MA_comm_port.conf -hide_banner -ignore_unknown -probesize 10000000 -analyzeduration 10000000 -loglevel verbose -async 1 -thread_queue_size 2048 -fflags +discardcorrupt+nobuffer -drop_second_field 0 -i - -filter_complex '[0:1]pan=stereo|c0=c0|c1=c1[a0];[0:1]pan=stereo|c0=c0|c1=c1[a1],[0:0]format=yuv420p,hwupload_cuda=device=0[video_upload];[video_upload]scale_npp=1920:1080:interp_algo=super,yadif_cuda=mode=0:deint=0[vout]' -aspect 16:9 -map [vout] -c:v:0 hevc_nvenc -gpu 0 -2pass 0 -b_ref_mode 0 -preset p7 -cbr 1 -rc:v:0 cbr -cbr_padding 1 -b:v:0 6000k -qmin:v:0 9 -qmax:v:0 21 -minrate:v:0 6000k -maxrate:v:0 6000k -bufsize:v:0 2000k -tune hq -r 25 -bsf:v hevc_mp4toannexb -flvflags no_duration_filesize -map [a0] -c:a:0 libfdk_aac -strict -2 -ac 2 -b:a:0 128k -map [a1] -c:a:1 libfdk_aac -strict -2 -ac 2 -b:a:1 128k -sn -metadata copyright='PikoTVEncoder' -metadata title='PikoTVEncoder' -keyint_min 50 -g 25 -f flv -y /tmp/out.flv
this works.

I use OSSRS SRS 7.0.147. If I use below command, command fails:

/opt/penc/sbin/bmdcapture --SIGTRAP --trap_nosignal 10 --sub_timeout -1 -m 10 -d 2 --portfile HEVC_RTMP_TEST_MA_port.conf -s 16 -c 2 -C 0 -V 4 -A 2 -p 8 -F nut -o strict=experimental:syncpoints=none -f pipe:1 | /opt/ffmpeg/bin/ffmpeg -ppid /opt/penc/run/HEVC_RTMP_TEST_MA.pid -pikotv_portfile /opt/penc/run/HEVC_RTMP_TEST_MA_comm_port.conf -hide_banner -ignore_unknown -probesize 10000000 -analyzeduration 10000000 -loglevel verbose -async 1 -thread_queue_size 2048 -fflags +discardcorrupt+nobuffer -drop_second_field 0 -i - -filter_complex '[0:1]pan=stereo|c0=c0|c1=c1[a0];[0:1]pan=stereo|c0=c0|c1=c1[a1],[0:0]format=yuv420p,hwupload_cuda=device=0[video_upload];[video_upload]scale_npp=1920:1080:interp_algo=super,yadif_cuda=mode=0:deint=0[vout]' -aspect 16:9 -map [vout] -c:v:0 hevc_nvenc -gpu 0 -2pass 0 -b_ref_mode 0 -preset p7 -cbr 1 -rc:v:0 cbr -cbr_padding 1 -b:v:0 6000k -qmin:v:0 9 -qmax:v:0 21 -minrate:v:0 6000k -maxrate:v:0 6000k -bufsize:v:0 2000k -tune hq -r 25 -bsf:v hevc_mp4toannexb -flvflags no_duration_filesize -map [a0] -c:a:0 libfdk_aac -strict -2 -ac 2 -b:a:0 128k -map [a1] -c:a:1 libfdk_aac -strict -2 -ac 2 -b:a:1 128k -sn -metadata copyright='PikoTVEncoder' -metadata title='PikoTVEncoder' -keyint_min 50 -g 25 -f flv 'rtmp://127.0.0.1/live/ch1'

It fails due to multiple (2) audio in stream. If I change endpoint to FFmpeg as RTMP listener, multitrack audio works.

[winlinvip]

Truth Record — 2026-07-26

• Issue: Multitrack Audio is not Supported #4681
• Verified: 2026-07-26
• Branch: develop
• Commit: 21f94c953735675f159405ba00f426c3f7e98305
• Version: SRS 8.0.4
• Environment: macOS 26.5.2, arm64; FFmpeg 8.1.1
• Supersedes: None
• Changes and tests: No project change. Reproduced with one H.264 video track and two AAC audio tracks.

Current state

SRS does not currently support Enhanced RTMP v2 multitrack audio. Publishing a stream containing Enhanced RTMP v2 audio headers causes SRS to reject SoundFormat=9 as unsupported.

The limitation exists in both the reported SRS 7.0.147 source and the current SRS 8.0.4 source. The current media model maintains one audio codec, parser, and sequence header per live stream and has no per-track state.

The targeted reproduction generated a two-second FLV stream containing one H.264 video track and two independent AAC audio tracks. ffprobe confirmed all three tracks. Publishing it to the locally built SRS 8.0.4 terminated the publisher with Broken pipe; SRS reported:

rtmp: consume audio : format consume audio : unsupported audio codec=9(Other)

FFmpeg 8 supports multitrack audio and video using Enhanced FLV v2. In the Enhanced RTMP v2 specification, SoundFormat=9 identifies the extended audio header used for features including multitrack audio:

• https://github.com/FFmpeg/FFmpeg/blob/master/Changelog
• https://github.com/veovera/enhanced-rtmp/blob/main/docs/enhanced/enhanced-rtmp-v2.md

Project direction

Enhanced RTMP v2 multitrack support is a valuable feature that SRS intends to support in the future. It belongs to the same class of substantial protocol work as Media over QUIC and other next-generation media protocols.

This feature is not the current priority. SRS is presently refining its code structure, documentation, knowledge base, development methods, and verification workflows so that AI can reliably manage and maintain the project.

After this AI-maintenance foundation is mature, the project can revisit Enhanced RTMP v2 and other major protocol features.

Conclusion

This is a valid future feature request, not a regression bug. Keep the issue open for future consideration. No immediate project change is required.