Re: [FFmpeg-devel] [PATCH 1/1] add option in file.c: pkt_size to setmax_packet_size

Wed, 30 Jul 2025 22:48:03 -0700 

This modification references the max_packet_size assignment method in other 
protocols, such as the one in udp.c；
This operation not only maintains the original setting but also adds custom 
settings；
For example, when reading a local file, you can first set pkt_size using 
av_dict_set and then pass the option in avio_open2；
This is mainly to deal with the situation where the IoT device has small 
memory, so that max_packet_size can be customized；


> ---
> libavformat/file.c | 4 +++-
> 1 file changed, 3 insertions(+), 1 deletion(-)
> 
> diff --git a/libavformat/file.c b/libavformat/file.c
> index 6a66040b65..8099a7e931 100644
> --- a/libavformat/file.c
> +++ b/libavformat/file.c
> @@ -94,6 +94,7 @@ typedef struct FileContext {
>     int fd;
>     int trunc;
>     int blocksize;
> +    int pkt_size;
>     int follow;
>     int seekable;
> #if HAVE_DIRENT_H
> @@ -106,6 +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 file 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 },
>     { NULL }
> };
> 
> @@ -313,7 +315,7 @@ 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 
= 262144;
> +        h->min_packet_size = h->max_packet_size 
= c->pkt_size;


What's the use case?




1+1=10
1441923...@qq.com



        



         原始邮件
         
       
发件人：Zhao Zhili <quinkbl...@foxmail.com&gt;
发件时间：2025年7月17日 23:01
收件人：FFmpeg development discussions and patches <ffmpeg-devel@ffmpeg.org&gt;
抄送：1441923451 <1441923...@qq.com&gt;
主题：Re: [FFmpeg-devel] [PATCH 1/1] add option in file.c: pkt_size to 
setmax_packet_size





&gt;&nbsp;On&nbsp;Jul&nbsp;17,&nbsp;2025,&nbsp;at&nbsp;22:05,&nbsp;yangsen5&nbsp;via&nbsp;ffmpeg-devel&nbsp;<ffmpeg-devel@ffmpeg.org&gt;&nbsp;wrote:
&gt;&nbsp;
&gt;&nbsp;From:&nbsp;yangsen5&nbsp;<1441923...@qq.com&gt;
&gt;&nbsp;
&gt;&nbsp;Signed-off-by:&nbsp;yangsen5&nbsp;<1441923...@qq.com&gt;
&gt;&nbsp;---
&gt;&nbsp;libavformat/file.c&nbsp;|&nbsp;4&nbsp;+++-
&gt;&nbsp;1&nbsp;file&nbsp;changed,&nbsp;3&nbsp;insertions(+),&nbsp;1&nbsp;deletion(-)
&gt;&nbsp;
&gt;&nbsp;diff&nbsp;--git&nbsp;a/libavformat/file.c&nbsp;b/libavformat/file.c
&gt;&nbsp;index&nbsp;6a66040b65..8099a7e931&nbsp;100644
&gt;&nbsp;---&nbsp;a/libavformat/file.c
&gt;&nbsp;+++&nbsp;b/libavformat/file.c
&gt;&nbsp;@@&nbsp;-94,6&nbsp;+94,7&nbsp;@@&nbsp;typedef&nbsp;struct&nbsp;FileContext&nbsp;{
&gt;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;int&nbsp;fd;
&gt;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;int&nbsp;trunc;
&gt;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;int&nbsp;blocksize;
&gt;&nbsp;+&nbsp;&nbsp;&nbsp;&nbsp;int&nbsp;pkt_size;
&gt;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;int&nbsp;follow;
&gt;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;int&nbsp;seekable;
&gt;&nbsp;#if&nbsp;HAVE_DIRENT_H
&gt;&nbsp;@@&nbsp;-106,6&nbsp;+107,7&nbsp;@@&nbsp;static&nbsp;const&nbsp;AVOption&nbsp;file_options[]&nbsp;=&nbsp;{
&gt;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;{&nbsp;"blocksize",&nbsp;"set&nbsp;I/O&nbsp;operation&nbsp;maximum&nbsp;block&nbsp;size",&nbsp;offsetof(FileContext,&nbsp;blocksize),&nbsp;AV_OPT_TYPE_INT,&nbsp;{&nbsp;.i64&nbsp;=&nbsp;INT_MAX&nbsp;},&nbsp;1,&nbsp;INT_MAX,&nbsp;AV_OPT_FLAG_ENCODING_PARAM&nbsp;},
&gt;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;{&nbsp;"follow",&nbsp;"Follow&nbsp;a&nbsp;file&nbsp;as&nbsp;it&nbsp;is&nbsp;being&nbsp;written",&nbsp;offsetof(FileContext,&nbsp;follow),&nbsp;AV_OPT_TYPE_INT,&nbsp;{&nbsp;.i64&nbsp;=&nbsp;0&nbsp;},&nbsp;0,&nbsp;1,&nbsp;AV_OPT_FLAG_DECODING_PARAM&nbsp;},
&gt;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;{&nbsp;"seekable",&nbsp;"Sets&nbsp;if&nbsp;the&nbsp;file&nbsp;is&nbsp;seekable",&nbsp;offsetof(FileContext,&nbsp;seekable),&nbsp;AV_OPT_TYPE_INT,&nbsp;{&nbsp;.i64&nbsp;=&nbsp;-1&nbsp;},&nbsp;-1,&nbsp;0,&nbsp;AV_OPT_FLAG_DECODING_PARAM&nbsp;|&nbsp;AV_OPT_FLAG_ENCODING_PARAM&nbsp;},
&gt;&nbsp;+&nbsp;&nbsp;&nbsp;&nbsp;{&nbsp;"pkt_size",&nbsp;"Maximum&nbsp;file&nbsp;packet&nbsp;size",&nbsp;offsetof(FileContext,&nbsp;pkt_size),&nbsp;AV_OPT_TYPE_INT,&nbsp;{&nbsp;.i64&nbsp;=&nbsp;262144&nbsp;},&nbsp;-1,&nbsp;INT_MAX,&nbsp;AV_OPT_FLAG_DECODING_PARAM&nbsp;|&nbsp;AV_OPT_FLAG_ENCODING_PARAM&nbsp;},
&gt;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;{&nbsp;NULL&nbsp;}
&gt;&nbsp;};
&gt;&nbsp;
&gt;&nbsp;@@&nbsp;-313,7&nbsp;+315,7&nbsp;@@&nbsp;static&nbsp;int&nbsp;file_open(URLContext&nbsp;*h,&nbsp;const&nbsp;char&nbsp;*filename,&nbsp;int&nbsp;flags)
&gt;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;/*&nbsp;Buffer&nbsp;writes&nbsp;more&nbsp;than&nbsp;the&nbsp;default&nbsp;32k&nbsp;to&nbsp;improve&nbsp;throughput&nbsp;especially
&gt;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;*&nbsp;with&nbsp;networked&nbsp;file&nbsp;systems&nbsp;*/
&gt;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;if&nbsp;(!h-&gt;is_streamed&nbsp;&amp;&amp;&nbsp;flags&nbsp;&amp;&nbsp;AVIO_FLAG_WRITE)
&gt;&nbsp;-&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;h-&gt;min_packet_size&nbsp;=&nbsp;h-&gt;max_packet_size&nbsp;=&nbsp;262144;
&gt;&nbsp;+&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;h-&gt;min_packet_size&nbsp;=&nbsp;h-&gt;max_packet_size&nbsp;=&nbsp;c-&gt;pkt_size;

What's&nbsp;the&nbsp;use&nbsp;case?

&gt;&nbsp;
&gt;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;if&nbsp;(c-&gt;seekable&nbsp;&gt;=&nbsp;0)
&gt;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;h-&gt;is_streamed&nbsp;=&nbsp;!c-&gt;seekable;
&gt;&nbsp;--&nbsp;
&gt;&nbsp;2.34.1
&gt;&nbsp;
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