Hi,
Le 17/12/2014 22:15, Reimar Döffinger a écrit :
On Wed, Dec 17, 2014 at 11:55:17AM +0100, Thomas Volkert wrote:
On 12/16/2014 08:36 AM, Reimar Döffinger wrote:
On Mon, Dec 15, 2014 at 10:24:55AM +0000, Carl Eugen Hoyos wrote:
codec->sample_rate = avio_rl32(pb);
codec->bit_rate = avio_rl32(pb) * 8;
codec->block_align = avio_rl16(pb);
+ if (big_endian) {
+ id = ntohs(id);
+ codec->channels = ntohs(codec->channels);
+ codec->sample_rate = ntohl(codec->sample_rate);
+ codec->bit_rate = ntohl(codec->bit_rate / 8) * 8;
+ codec->block_align = ntohs(codec->block_align);
+ }
Instead please do:
if (big_endian) {
id = avio_rb32(pb);
codec->channels = avio_rb32(pb);
...
} else {
id = avio_rl32(pb);
...
}
Not sure this is a good idea, as it duplicates the code.
It might be better to use the if as-is, just replacing ntoh*
by av_bswap*.
I would prefer this version:
if (!big_endian) {
avio_rl32()
} else {
avio_rb32()
}
In case of big endianess, your idea (and my former solution) would need two
instead of one updates per value
Why would that matter? Performance, especially for big-endian type is
hardly relevant.
Due to fewer branches it might actually give better performance for the
common case (but as said I don't think it matters).
It mostly avoids duplicating some actual code like the *8.
There are also other options to reduce the code size, though I am
sceptical if they are a good idea.
1) Macros like:
#define GET16(pb) (big_endian ? avio_rb16(pb) : avio_rl16(pb))
2) Functions that take an additional endian argument.
While we're at it:
3) Function pointers initialized based on the endianness
--
Ben
_______________________________________________
ffmpeg-devel mailing list
ffmpeg-devel@ffmpeg.org
http://ffmpeg.org/mailman/listinfo/ffmpeg-devel
