[FFmpeg-devel] [PATCH] libavformat/file: allow configurable pkt_size for lower memory usage on embedded devices (PR #21004)

[caifan via ffmpeg-devel <ffmpeg-devel@ffmpeg.org>]

PR #21004 opened by caifan
URL: https://code.ffmpeg.org/FFmpeg/FFmpeg/pulls/21004
Patch URL: https://code.ffmpeg.org/FFmpeg/FFmpeg/pulls/21004.patch

This change lets embedded systems reduce memory usage by adjusting pkt_size
through options. The code now applies pkt_size to both read and write cases.
This makes the file protocol more flexible on devices with limited RAM.

Signed-off-by: caifan3 <caifan3@xiaomi.com>


>From cb04a6c7ae0b65a97f8dae06e3557acce6d48fe3 Mon Sep 17 00:00:00 2001
From: caifan3 <caifan3@xiaomi.com>
Date: Mon, 24 Nov 2025 20:59:54 +0800
Subject: [PATCH] libavformat/file: allow configurable pkt_size for lower
 memory usage on embedded devices

This change lets embedded systems reduce memory usage by adjusting pkt_size
through options. The code now applies pkt_size to both read and write cases.
This makes the file protocol more flexible on devices with limited RAM.

Signed-off-by: caifan3 <caifan3@xiaomi.com>
---
 libavformat/file.c | 9 ++++++---
 1 file changed, 6 insertions(+), 3 deletions(-)

diff --git a/libavformat/file.c b/libavformat/file.c
index 97f5955f93..429ea644d7 100644
--- a/libavformat/file.c
+++ b/libavformat/file.c
@@ -107,7 +107,7 @@ static const AVOption file_options[] = {
     { "blocksize", "set I/O operation maximum block size", offsetof(FileContext, blocksize), AV_OPT_TYPE_INT, { .i64 = INT_MAX }, 1, INT_MAX, AV_OPT_FLAG_ENCODING_PARAM },
     { "follow", "Follow a file as it is being written", offsetof(FileContext, follow), AV_OPT_TYPE_INT, { .i64 = 0 }, 0, 1, AV_OPT_FLAG_DECODING_PARAM },
     { "seekable", "Sets if the file is seekable", offsetof(FileContext, seekable), AV_OPT_TYPE_INT, { .i64 = -1 }, -1, 0, AV_OPT_FLAG_DECODING_PARAM | AV_OPT_FLAG_ENCODING_PARAM },
-    { "pkt_size", "Maximum packet size", offsetof(FileContext, pkt_size), AV_OPT_TYPE_INT, { .i64 = 262144 }, 1, INT_MAX, AV_OPT_FLAG_DECODING_PARAM | AV_OPT_FLAG_ENCODING_PARAM },
+    { "pkt_size", "Maximum packet size", offsetof(FileContext, pkt_size), AV_OPT_TYPE_INT, { .i64 = 0 }, 1, INT_MAX, AV_OPT_FLAG_DECODING_PARAM | AV_OPT_FLAG_ENCODING_PARAM },
     { NULL }
 };
 
@@ -314,8 +314,11 @@ static int file_open(URLContext *h, const char *filename, int flags)
 
     /* Buffer writes more than the default 32k to improve throughput especially
      * with networked file systems */
-    if (!h->is_streamed && flags & AVIO_FLAG_WRITE)
-        h->min_packet_size = h->max_packet_size = c->pkt_size;
+    if (!h->is_streamed && (flags & AVIO_FLAG_WRITE))
+        h->min_packet_size = h->max_packet_size = c->pkt_size ? c->pkt_size : 262144;
+
+    if (!h->is_streamed && (flags & AVIO_FLAG_READ))
+        h->min_packet_size = h->max_packet_size = c->pkt_size ? c->pkt_size : 32768;
 
     if (c->seekable >= 0)
         h->is_streamed = !c->seekable;
-- 
2.49.1

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