AnyPS5/docs/dev/debt/libSceAudiodec.md

libSceAudiodec technical debt

Unknown function info

• M4AAC extended parameters: 28-byte and 32-byte parameter variants add fields at offsets 24 and 28, named by their range errors (0x807F0305 SCE_AUDIODEC_ERROR_M4AAC_INVALID_ENABLE_NONDELAY_OUTPUT, 0x807F0306 SCE_AUDIODEC_ERROR_M4AAC_INVALID_SURROUND_CHANNEL_INTERLEAVE_ORDER, in fpPS4's ps4_libsceaudiodec.pas). Non-delay output 1 decodes every access unit to its own PCM from the first one on, as shadPS4's AJM AAC decoder does with EnableNondelayOutput; without that flag shadPS4 holds back the first 2 frames. Non-delay output 0 still decodes the same way, with no frame held back: no measurement shows whether the console delays it. Interleave orders 1 and 2 leave mono and stereo output unchanged, having no surround channels to place (PPSA21607 decodes stereo with order 2); with more channels they throw: no source says which value selects shadPS4's ExtlExtrLsRs or LsRsExtlExtr AJM order, or which order 0 is.

• sceAudiodecDecode (libSceAudiodec) - a raw M4AAC stream carries no channel configuration, so the decoder tries the mono/stereo configuration and then configurations 3 to 7 within ui_max_channels until one decodes the first access unit, and keeps that one. No reference documents how the library picks the layout (shadPS4 maps the channel count straight to the configuration; SharpProspero only describes the maximum). With the stereo configuration a mono raw stream decodes as 2 channels, so 2 is reported, not 1

• sceAudiodecDecode (libSceAudiodec) - the HE-AAC handling follows one console measurement of an HE-AAC v2 ADTS stream: SBR output at 48 kHz in one channel with ui_enable_heaac 1, the 24 kHz mono core with 0. Not measured: whether the console, like FFmpeg, decodes a stream without SBR data in its first access unit as AAC-LC with ui_enable_heaac 1, and what it reports in ui_sampling_freq and ui_heaac with ui_enable_heaac 0 (here the rate of the returned PCM and 0)

Functional

• sceAudiodecDecode (libSceAudiodec) - an ADTS stream with channel configuration 0 (layout in a program config element) is still parsed by FFmpeg, so ui_enable_heaac 0 does not remove its SBR and a mono one with Parametric Stereo comes out as stereo.
• libSceAudiodec accepts only 16-bit PCM, and float PCM for ATRAC9 and M4AAC, as sceAudiodecCreateDecoder did in a payload process on a PS5 (firmware 13.60), which returned ERROR_INVALID_WORD_LENGTH for iBwPcm 0, 3 and -1 with each codec and for float with MP3; other word sizes are assumed to fail the same way. Separately measured on PS4 (firmware 10.71) for MP3 and M4AAC over iBwPcm -1 to 3: MP3 accepts only 16-bit (1), M4AAC accepts 16-bit and float (1 and 2), and every other value returns ERROR_INVALID_WORD_LENGTH. ATRAC9's word length is not reached there: with invalid config data the console returns ERROR_AT9_INVALID_CONFIG_DATA for every word length, so it validates the config before the word size. This is a PS4 10.71 measurement; the PS5 behaviour for these cases is still the 13.60 one above, not re-confirmed on current PS5 firmware. ATRAC9 decoding is covered only by configuration and error tests, as no ATRAC9 encoder is available for a fixture.