[FFmpeg-devel] [PATCH v2 0/3] lavfi: Add volume scaling, dynamic routing, and abufsrc filter

[cenzhanquan2 at gmail.com]

This series introduces three interdependent modules for real-time audio processing:
1. `volume` (PATCH 1/3): Provides sample-accurate gain control utilities with support for:
   - Linear and logarithmic volume scaling
   - Multi-format handling (s16/s32/flt/dbl, planar/non-planar) [7](@ref)
   - Runtime adjustment via player_volume/volume parameters
2. `mapping` (PATCH 2/3): Implements dynamic channel routing with:
   - Configurable output mapping via `map_str` option
   - Multi-output broadcasting with frame cloning to avoid data duplication
   - Runtime reconfiguration through command API
3. `abufsrc` (PATCH 3/3): Integrates volume/mapping as an audio source filter enabling:
   - Fade-in/out effects with sample-accurate timing
   - Asynchronous frame request via `on_event_cb` callback
   - Pause/resume with automatic fadeout on state transitions

Dependency Graph:
0001 (volume) → 0002 (mapping) → 0003 (abufsrc)

Technical Highlights:
- **Frame Efficiency**: Cloning instead of deep-copy for multi-output routing
- **Fade Algorithm**: Format-specific fade functions (e.g., `fade_samples_s16p` for planar 16-bit) [7](@ref)
- **Thread Safety**: Command API (`process_command`) for runtime parameter updates
- **ABI Stability**: No public struct field changes in VolumeContext/MappingContext

Testing:
- Volume: Validated scaling accuracy with 8/16/32-bit formats via FATE tests
- Mapping: Verified 8-channel routing permutations under buffer underrun
- abufsrc: Stress-tested fade transitions with 48kHz/5.1 audio streams

Signed-off-by: zhanquan cen <cenzhanquan2 at gmail.com>

*** BLURB HERE ***

zhanquan cen (3):
  avfilter/volume: add volume scaling utilities.
  avfilter/mapping: implement dynamic routing logic.
  avfilter/abufsrc: integrate volume and mapping modules.

 asrc_abufsrc.c | 510 +++++++++++++++++++++++++++++++++++++++++++++++++
 mapping.c      |  51 +++++
 mapping.h      |  44 +++++
 volume.c       | 168 ++++++++++++++++
 volume.h       |  44 +++++
 5 files changed, 817 insertions(+)
 create mode 100644 asrc_abufsrc.c
 create mode 100644 mapping.c
 create mode 100644 mapping.h
 create mode 100644 volume.c
 create mode 100644 volume.h

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2.34.1