[FFmpeg-devel] [PATCH] avcodec/liblc3enc: Avoid allocating buffer to send a zero frame (PR #20633)

[FFmpeg-devel] [PATCH] avcodec/liblc3enc: Avoid allocating buffer to send a zero frame (PR #20633)

[mkver via ffmpeg-devel]

PR #20633 opened by mkver
URL: https://code.ffmpeg.org/FFmpeg/FFmpeg/pulls/20633
Patch URL: https://code.ffmpeg.org/FFmpeg/FFmpeg/pulls/20633.patch

liblc3 supports arbitrary strides, so one can simply use a stride
of zero to make it read the same zero value again and again.


>From 3bf38a3570673776249787228325a8c15bc020c6 Mon Sep 17 00:00:00 2001
From: Andreas Rheinhardt <andreas.rheinhardt@outlook.com>
Date: Tue, 30 Sep 2025 18:53:08 +0200
Subject: [PATCH] avcodec/liblc3enc: Avoid allocating buffer to send a zero
 frame

liblc3 supports arbitrary strides, so one can simply use a stride
of zero to make it read the same zero value again and again.

Signed-off-by: Andreas Rheinhardt <andreas.rheinhardt@outlook.com>
---
 libavcodec/liblc3enc.c | 12 +++---------
 1 file changed, 3 insertions(+), 9 deletions(-)

diff --git a/libavcodec/liblc3enc.c b/libavcodec/liblc3enc.c
index 66007a90f3..72c117b993 100644
--- a/libavcodec/liblc3enc.c
+++ b/libavcodec/liblc3enc.c
@@ -137,7 +137,6 @@ static int liblc3_encode(AVCodecContext *avctx, AVPacket *pkt,
     LibLC3EncContext *liblc3 = avctx->priv_data;
     int block_bytes = liblc3->block_bytes;
     int channels = avctx->ch_layout.nb_channels;
-    void *zero_frame = NULL;
     uint8_t *data_ptr;
     int ret;
 
@@ -152,25 +151,20 @@ static int liblc3_encode(AVCodecContext *avctx, AVPacket *pkt,
             return 0;
 
         liblc3->remaining_samples = 0;
-        zero_frame = av_mallocz(avctx->frame_size * sizeof(float));
-        if (!zero_frame)
-            return AVERROR(ENOMEM);
     }
 
     data_ptr = pkt->data;
     for (int ch = 0; ch < channels; ch++) {
-        const float *pcm = zero_frame ? zero_frame : frame->data[ch];
+        const float *pcm = frame ? (const float*)frame->data[ch] : (const float[]){ 0 };
+        int stride = !!frame; // use a stride of zero to send a zero frame
         int nbytes = block_bytes / channels + (ch < block_bytes % channels);
 
         lc3_encode(liblc3->encoder[ch],
-                   LC3_PCM_FORMAT_FLOAT, pcm, 1, nbytes, data_ptr);
+                   LC3_PCM_FORMAT_FLOAT, pcm, stride, nbytes, data_ptr);
 
         data_ptr += nbytes;
     }
 
-    if (zero_frame)
-        av_free(zero_frame);
-
     *got_packet_ptr = 1;
 
     return 0;
-- 
2.49.1

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