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new 82144fea48 libavformat/file: apply pkt_size option to read mode
82144fea48 is described below
commit 82144fea488387539d7008bef5cdbf52ccbc6113
Author: caifan3 <[email protected]>
AuthorDate: Mon Dec 22 14:32:00 2025 +0800
Commit: Marton Balint <[email protected]>
CommitDate: Tue Dec 30 00:49:13 2025 +0000
libavformat/file: apply pkt_size option to read mode
Previously, the pkt_size option only affected write buffering in the file
protocol. This change extends its effect to read mode as well.
On embedded systems with limited RAM, users can now reduce I/O buffer
memory by setting a smaller pkt_size.
Signed-off-by: caifan3 <[email protected]>
---
doc/protocols.texi | 9 +++++++++
libavformat/file.c | 10 +++++++---
2 files changed, 16 insertions(+), 3 deletions(-)
diff --git a/doc/protocols.texi b/doc/protocols.texi
index dee2b845ac..b5330a1160 100644
--- a/doc/protocols.texi
+++ b/doc/protocols.texi
@@ -352,6 +352,15 @@ means auto (seekable for normal files, non-seekable for
named pipes).
Many demuxers handle seekable and non-seekable resources differently,
overriding this might speed up opening certain files at the cost of losing some
features (e.g. accurate seeking).
+
+@item pkt_size
+Set the maximum packet size used for file I/O.
+
+For writing, this sets the size of each write operation. The default is
+262144 bytes.
+For reading, if explicitly set, it overrides the default internal buffer size
+(32768 bytes) and limits the maximum amount of data read per operation.
+Setting a smaller value may reduce memory usage when reading files
sequentially.
@end table
@section ftp
diff --git a/libavformat/file.c b/libavformat/file.c
index 97f5955f93..23dc7081d3 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 }, 0, INT_MAX, AV_OPT_FLAG_DECODING_PARAM |
AV_OPT_FLAG_ENCODING_PARAM },
{ NULL }
};
@@ -314,8 +314,12 @@ 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) {
+ if (flags & AVIO_FLAG_WRITE)
+ h->min_packet_size = h->max_packet_size = c->pkt_size ?
c->pkt_size : 262144;
+ else if (flags & AVIO_FLAG_READ && c->pkt_size)
+ h->max_packet_size = c->pkt_size;
+ }
if (c->seekable >= 0)
h->is_streamed = !c->seekable;
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