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avcodec/ttmlenc: Don't copy data around unnecessarily 

Using av_bprint_init_for_buffer() avoids copying data
into the internal AVBPrint buffer (or worse: to allocate
a temporary buffer in case the internal buffer does not
suffice).

Signed-off-by: Andreas Rheinhardt <andreas.rheinhardt@outlook.com>
This commit is contained in:
Andreas Rheinhardt 2024-02-18 01:23:26 +01:00
parent abea3749b3
commit 253a8340f5
1 changed files with 16 additions and 20 deletions
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36
libavcodec/ttmlenc.c
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@ -29,11 +29,9 @@
#include "avcodec.h"
#include "codec_internal.h"
#include "libavutil/avstring.h"
#include "libavutil/bprint.h"
#include "libavutil/internal.h"
#include "ass_split.h"
#include "ass.h"
#include "ttmlenc.h"
typedef struct {
@ -84,7 +82,7 @@ static int ttml_encode_frame(AVCodecContext *avctx, uint8_t *buf,
ASSDialog *dialog;
int i;
av_bprint_clear(&s->buffer);
av_bprint_init_for_buffer(&s->buffer, buf, bufsize);
for (i=0; i<sub->num_rects; i++) {
const char *ass = sub->rects[i]->ass;
@ -129,14 +127,9 @@ static int ttml_encode_frame(AVCodecContext *avctx, uint8_t *buf,
ff_ass_free_dialog(&dialog);
}
if (!av_bprint_is_complete(&s->buffer))
return AVERROR(ENOMEM);
if (!s->buffer.len)
return 0;
// force null-termination, so in case our destination buffer is
// too small, the return value is larger than bufsize minus null.
if (av_strlcpy(buf, s->buffer.str, bufsize) > bufsize - 1) {
if (!av_bprint_is_complete(&s->buffer)) {
av_log(avctx, AV_LOG_ERROR, "Buffer too small for TTML event.\n");
return AVERROR_BUFFER_TOO_SMALL;
}
@ -150,8 +143,6 @@ static av_cold int ttml_encode_close(AVCodecContext *avctx)
ff_ass_split_free(s->ass_ctx);
av_bprint_finalize(&s->buffer, NULL);
return 0;
}
@ -306,6 +297,7 @@ static int ttml_write_header_content(AVCodecContext *avctx)
const size_t base_extradata_size = TTMLENC_EXTRADATA_SIGNATURE_SIZE + 1 +
AV_INPUT_BUFFER_PADDING_SIZE;
size_t additional_extradata_size = 0;
int ret;
if (script_info.play_res_x <= 0 || script_info.play_res_y <= 0) {
av_log(avctx, AV_LOG_ERROR,
@ -314,6 +306,8 @@ static int ttml_write_header_content(AVCodecContext *avctx)
return AVERROR_INVALIDDATA;
}
av_bprint_init(&s->buffer, 0, INT_MAX - base_extradata_size);
// write the first string in extradata, attributes in the base "tt" element.
av_bprintf(&s->buffer, TTML_DEFAULT_NAMESPACING);
// the cell resolution is in character cells, so not exactly 1:1 against
@ -329,10 +323,10 @@ static int ttml_write_header_content(AVCodecContext *avctx)
av_bprintf(&s->buffer, " <layout>\n");
for (int i = 0; i < ass->styles_count; i++) {
int ret = ttml_write_region(avctx, &s->buffer, script_info,
ass->styles[i]);
ret = ttml_write_region(avctx, &s->buffer, script_info,
ass->styles[i]);
if (ret < 0)
return ret;
goto fail;
}
av_bprintf(&s->buffer, " </layout>\n");
@ -340,14 +334,16 @@ static int ttml_write_header_content(AVCodecContext *avctx)
av_bprint_chars(&s->buffer, '\0', 1);
if (!av_bprint_is_complete(&s->buffer)) {
return AVERROR(ENOMEM);
ret = AVERROR(ENOMEM);
goto fail;
}
additional_extradata_size = s->buffer.len;
if (!(avctx->extradata =
av_mallocz(base_extradata_size + additional_extradata_size))) {
return AVERROR(ENOMEM);
ret = AVERROR(ENOMEM);
goto fail;
}
avctx->extradata_size =
@ -359,9 +355,11 @@ static int ttml_write_header_content(AVCodecContext *avctx)
memcpy(avctx->extradata + TTMLENC_EXTRADATA_SIGNATURE_SIZE,
s->buffer.str, additional_extradata_size);
av_bprint_clear(&s->buffer);
ret = 0;
fail:
av_bprint_finalize(&s->buffer, NULL);
return 0;
return ret;
}
static av_cold int ttml_encode_init(AVCodecContext *avctx)
@ -370,8 +368,6 @@ static av_cold int ttml_encode_init(AVCodecContext *avctx)
int ret = AVERROR_BUG;
s->avctx = avctx;
av_bprint_init(&s->buffer, 0, AV_BPRINT_SIZE_UNLIMITED);
if (!(s->ass_ctx = ff_ass_split(avctx->subtitle_header))) {
return AVERROR_INVALIDDATA;
}