From d1c8d45d5dc8ae09f03e2f0a9c6b3ac1910b8cdc Mon Sep 17 00:00:00 2001 From: Luke Hoersten Date: Sat, 20 Jun 2026 20:50:43 -0500 Subject: firmware: split stream recv into its own task with 3-buffer ping-pong MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit handle_client previously ran recv → decode → paint serially on one FreeRTOS task. The kernel TCP buffer filled during decode+paint (~6ms), and against the IDF-default 5760-byte window the sender naturally stop-go-rate-limited to ~consumption. Raising the window to 65535 (previous experiment) regressed g2g from ~100ms to 17s growing unbounded — the sender pumped 45+ segments per round into a kernel buffer the app couldn't drain in time, and there was no way to skip-oldest on the kernel queue. This commit decouples recv from decode+paint: recv-task: owns the socket. Reads header + body into one of three preallocated PSRAM body buffers. On body complete, swaps the just-filled buffer into a 1-deep pending slot and picks a free buffer for the next recv. If the slot already held a frame (decode is slow), drops oldest in place — mirror of the Scrypted-side skip-oldest from e5acf93. decode-task: waits on a binary semaphore. On signal, claims pending, then decodes + paints without holding any shared lock. Frees its prior buffer implicitly by overwriting s_decode_idx on the next claim. 3 PSRAM body buffers (~3MB of 28MB free) ensure the invariant {recv_idx, pending_idx, decode_idx} are pairwise distinct without ever blocking recv. jpeg_decoder.c grew an alloc_input_buffer helper + jpeg_decoder_decode now takes an explicit input pointer so the stream and http_api snapshot paths don't share scratch. New stats: - recv_dropped_oldest: per-window count of pending-slot overwrites - decode_idle_min/avg/max_us: time decode-task spent waiting on signal Measurement at IDF-default 5760 window, Unifi medium substream: before split: recv_avg=32ms recv_max~44ms fps=22-26 (recv blocked during 6ms decode+paint; chunk_max capped at 5760) after split: recv_avg=17ms recv_max=18-37ms fps=21-29 steady, decode_idle_avg=27-40ms (decode mostly waiting), drop_oldest=0, painted at source rate The bottleneck moved from 'decode+paint serializes recv' to the wire's own send rate. Bigger windows are now safe (recv-task drains continuously, can't bury us), but won't add fps until source rate goes up — that's a separate conversation. --- main/jpeg_decoder.h | 30 ++++++++++++++++++++++-------- 1 file changed, 22 insertions(+), 8 deletions(-) (limited to 'main/jpeg_decoder.h') diff --git a/main/jpeg_decoder.h b/main/jpeg_decoder.h index e8a8504..495b1a5 100644 --- a/main/jpeg_decoder.h +++ b/main/jpeg_decoder.h @@ -19,20 +19,34 @@ esp_err_t jpeg_decoder_init(void); bool jpeg_decoder_try_lock(uint32_t timeout_ms); void jpeg_decoder_unlock(void); -// Pointer to the input scratch buffer (PSRAM, DMA-aligned). Capacity = -// JPEG_DECODER_MAX_INPUT_BYTES. Caller fills before calling decode. +// Pointer to the built-in input scratch buffer (PSRAM, DMA-aligned). +// Capacity = JPEG_DECODER_MAX_INPUT_BYTES. Owned by the decoder. +// http_api's snapshot path fills this and decodes from it. The stream +// server allocates its own buffers via jpeg_decoder_alloc_input_buffer. void *jpeg_decoder_input_buffer(void); -// Decode the JPEG sitting in the input buffer into the caller-provided -// out_buf (must be at least out_cap bytes, ≥ 800*480*3 for a full -// panel-sized frame). Bytes land in BGR memory order so the DSI engine -// + TC358762 + Pi panel render channels correctly. Reports image -// width/height in pixels. +// Allocate an additional DMA-aligned PSRAM input buffer suitable for +// jpeg_decoder_decode. Capacity reported via *out_cap. Returned pointer +// is owned by the caller and never freed — call once per buffer at +// init time. NULL on failure. +// +// Used by the stream server to maintain a ping-pong ring of body +// buffers between its recv task and its decode/paint task — recv +// fills one buffer while decode processes another, no memcpy on +// handoff. +void *jpeg_decoder_alloc_input_buffer(size_t *out_cap); + +// Decode the JPEG sitting in in_buf into the caller-provided out_buf +// (must be at least out_cap bytes, ≥ 800*480*3 for a full panel-sized +// frame). Bytes land in BGR memory order so the DSI engine + TC358762 +// + Pi panel render channels correctly. Reports image width/height +// in pixels. // // In the /frame hot path the caller passes display_back_buffer() so // the hardware decoder writes pixels straight into the panel's back // framebuffer with zero intermediate copies. -esp_err_t jpeg_decoder_decode(size_t jpeg_len, +esp_err_t jpeg_decoder_decode(void *in_buf, + size_t jpeg_len, void *out_buf, size_t out_cap, uint16_t *out_width, -- cgit v1.2.3