Re: [FFmpeg-devel] [PATCH] avformat/avio: Add max_pkt_size option

[Zhao Zhili <quinkblack-at-foxmail.com@ffmpeg.org>]

> On Mar 14, 2025, at 04:03, Marton Balint <cus@passwd.hu> wrote:
> 
> 
> On Thu, 13 Mar 2025, Zhao Zhili wrote:
> 
>> From: Zhao Zhili <zhilizhao@tencent.com>
>> 
>> Optimizing memory footprint in memory-constrained systems.
>> 
>> Signed-off-by: Zhao Zhili <zhilizhao@tencent.com>
>> ---
>> libavformat/avio.c    | 2 ++
>> libavformat/version.h | 2 +-
>> 2 files changed, 3 insertions(+), 1 deletion(-)
>> 
>> diff --git a/libavformat/avio.c b/libavformat/avio.c
>> index d109f3adff..e1b959ed73 100644
>> --- a/libavformat/avio.c
>> +++ b/libavformat/avio.c
>> @@ -61,6 +61,8 @@ static const AVOption options[] = {
>>    {"protocol_whitelist", "List of protocols that are allowed to be used", OFFSET(protocol_whitelist), AV_OPT_TYPE_STRING, { .str = NULL },  0, 0, D },
>>    {"protocol_blacklist", "List of protocols that are not allowed to be used", OFFSET(protocol_blacklist), AV_OPT_TYPE_STRING, { .str = NULL },  0, 0, D },
>>    {"rw_timeout", "Timeout for IO operations (in microseconds)", offsetof(URLContext, rw_timeout), AV_OPT_TYPE_INT64, { .i64 = 0 }, 0, INT64_MAX, AV_OPT_FLAG_ENCODING_PARAM | AV_OPT_FLAG_DECODING_PARAM },
>> +    {"max_pkt_size", "Default maximum packet size in bytes, could be overwritten by particular protocol",
>> +            offsetof(URLContext, max_packet_size), AV_OPT_TYPE_INT, { .i64 = IO_BUFFER_SIZE }, 0, INT_MAX, AV_OPT_FLAG_ENCODING_PARAM | AV_OPT_FLAG_DECODING_PARAM },
>>    { NULL }
>> };
> 
> 
> This feels super confusing. A *max_packet_size* option which might not do anything at all depending on the protocol the user is using, and which the user might override with the protocol specific *pkt_size* option if it exists. So I'd rather not expose ->max_pkt_size like that.

rw_timeout has the same issue, it’s still useful for users.

The patch is for 

https://ffmpeg.org/pipermail/ffmpeg-devel/2025-March/341114.html

We can add pkt_size for more protocols, but it sounds weird for tcp
with pkt_size option.

Use can change AVIOContext::max_packet_size directly. I’m not sure
if it’s better or valid.

> 
> Regards,
> Marton
> 
> 
>> 
>> diff --git a/libavformat/version.h b/libavformat/version.h
>> index 6ffdf61b43..e1ab967f5b 100644
>> --- a/libavformat/version.h
>> +++ b/libavformat/version.h
>> @@ -32,7 +32,7 @@
>> #include "version_major.h"
>> 
>> #define LIBAVFORMAT_VERSION_MINOR   9
>> -#define LIBAVFORMAT_VERSION_MICRO 107
>> +#define LIBAVFORMAT_VERSION_MICRO 108
>> 
>> #define LIBAVFORMAT_VERSION_INT AV_VERSION_INT(LIBAVFORMAT_VERSION_MAJOR, \
>>                                               LIBAVFORMAT_VERSION_MINOR, \
>> -- 
>> 2.46.0
>> 
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