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Code Issues Releases Activity

avformat/apngenc: Don't modify input packet

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It might not be writable at this point.

Signed-off-by: Andreas Rheinhardt <andreas.rheinhardt@outlook.com>
This commit is contained in:
Andreas Rheinhardt 2022-07-04 17:04:15 +02:00
parent f89446eaff
commit 05e96e6933
1 changed files with 13 additions and 4 deletions
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17
libavformat/apngenc.c
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@ -159,6 +159,7 @@ static int flush_packet(AVFormatContext *format_context, AVPacket *packet)
avio_write(io_context, apng->prev_packet->data, apng->prev_packet->size);
}
} else {
const uint8_t *data, *data_end;
uint8_t *existing_fcTL_chunk;
if (apng->frame_number == 0) {
@ -178,6 +179,8 @@ static int flush_packet(AVFormatContext *format_context, AVPacket *packet)
}
}
data = apng->prev_packet->data;
data_end = data + apng->prev_packet->size;
existing_fcTL_chunk = apng_find_chunk(MKBETAG('f', 'c', 'T', 'L'), apng->prev_packet->data, apng->prev_packet->size);
if (existing_fcTL_chunk) {
AVRational delay;
@ -190,6 +193,8 @@ static int flush_packet(AVFormatContext *format_context, AVPacket *packet)
delay.den = AV_RB16(existing_fcTL_chunk + 22);
if (delay.num == 0 && delay.den == 0) {
uint8_t new_fcTL_chunk[APNG_FCTL_CHUNK_SIZE];
if (packet) {
int64_t delay_num_raw = (packet->dts - apng->prev_packet->dts) * codec_stream->time_base.num;
int64_t delay_den_raw = codec_stream->time_base.den;
@ -205,16 +210,20 @@ static int flush_packet(AVFormatContext *format_context, AVPacket *packet)
delay = apng->prev_delay;
}
avio_write(io_context, data, (existing_fcTL_chunk - 8) - data);
data = existing_fcTL_chunk + APNG_FCTL_CHUNK_SIZE + 4 /* CRC-32 */;
// Update frame control header with new delay
AV_WB16(existing_fcTL_chunk + 20, delay.num);
AV_WB16(existing_fcTL_chunk + 22, delay.den);
AV_WB32(existing_fcTL_chunk + 26, ~av_crc(av_crc_get_table(AV_CRC_32_IEEE_LE), ~0U, existing_fcTL_chunk - 4, 26 + 4));
memcpy(new_fcTL_chunk, existing_fcTL_chunk, sizeof(new_fcTL_chunk));
AV_WB16(new_fcTL_chunk + 20, delay.num);
AV_WB16(new_fcTL_chunk + 22, delay.den);
apng_write_chunk(io_context, MKBETAG('f', 'c', 'T', 'L'),
new_fcTL_chunk, sizeof(new_fcTL_chunk));
}
apng->prev_delay = delay;
}
// Write frame data
avio_write(io_context, apng->prev_packet->data, apng->prev_packet->size);
avio_write(io_context, data, data_end - data);
}
++apng->frame_number;