Hello,
Due to memory usage, we need to use a buffered solution to load a small chunk
of blocks of streams in memory instead of loading the whole stream with:
avformat_network_init();
std::uint8_t *avioc_buffer =
static_cast<uint8_t *> (av_malloc(AV_BUFFER_BLOCK_SIZE));
avioc_ = avio_alloc_context(
avioc_buffer, AV_BUFFER_BLOCK_SIZE, 0, &data_provider_,
&ReadAVBlockCallback, nullptr, nullptr);
fmtc_ = avformat_alloc_context();
fmtc_->pb = avioc_[idx];
fmtc_->flags |= AVFMT_FLAG_CUSTOM_IO;
avformat_open_input(&fmtc_, nullptr, nullptr, nullptr);
ReadAVBlockCallback is the callback provided to refill the new block.
AV_BUFFER_BLOCK_SIZE is 8Mytes.
The issue is that I need to implement the seek feature with av_seek_frame API
and av_seek_frame is not calling the callback, "ReadAVBlockCallback" to fill
the buffer when needed if the frame to seek is not in the current buffer block.
I am using FFmpeg 4.1 (and the same issue in 4.4).
I've rebuilt FFmpeg to look at it with the debugger.
What I have observed is that:
"av_index_search_timestamp" call is looking at "stream's index_entries" and if
the entry for the seek point is found, and returned, it does not need to call
the callback to refill the "stream buffer".
But the problem is that this buffer does not have the packet with this seek
timestamp, therefore, it cannot seek to the correct keyframe.
Here is the code snap from matroskadec.c
if ((index = av_index_search_timestamp(st, timestamp, flags)) < 0 || index
== st->nb_index_entries - 1) { //if the index is valid, no need to refill the
stream buffer but the current buffer does not always have the target frame.
avio_seek(s->pb, st->index_entries[st->nb_index_entries - 1].pos,
SEEK_SET);
matroska->current_id = 0;
while ((index = av_index_search_timestamp(st, timestamp, flags)) < 0 ||
index == st->nb_index_entries - 1) {
matroska_clear_queue(matroska);
if (matroska_parse_cluster(matroska) < 0) // this is where the new
block is load
break;
}
}
Can you please let me know how I can fix it? Is there a solution in the new
releases?
Thank you, a lot.
[cid:[email protected]]
Baris Unal
Software Engineer III
[email protected]<mailto:[email protected]>
www.statsperform.com<http://www.statsperform.com>
This email is from Stats Perform. Perform Content Limited (Company No:
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