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Cleaning up seek code.
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Replacing pts calculation based on duration
with that based on fps for higher precision
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@rarzumanyan
rarzumanyan committed Jan 26, 2022
1 parent ec453ad commit e7ea766
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Showing 7 changed files with 180 additions and 112 deletions.
4 changes: 4 additions & 0 deletions PyNvCodec/TC/inc/FFmpegDemuxer.h
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Original file line number Diff line number Diff line change
Expand Up @@ -222,6 +222,10 @@ class DllExport FFmpegDemuxer

double GetTimebase() const;

int64_t TsFromTime(double ts_sec);

int64_t TsFromFrameNumber(int64_t frame_num);

uint32_t GetVideoStreamIndex() const;

AVPixelFormat GetPixelFormat() const;
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2 changes: 2 additions & 0 deletions PyNvCodec/TC/inc/Tasks.hpp
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Original file line number Diff line number Diff line change
Expand Up @@ -221,6 +221,8 @@ class DllExport DemuxFrame final : public Task
DemuxFrame& operator=(const DemuxFrame& other) = delete;

void GetParams(struct MuxingParams& params) const;
int64_t TsFromTime(double ts_sec);
int64_t TsFromFrameNumber(int64_t frame_num);
void Flush();
TaskExecStatus Run() final;
~DemuxFrame() final;
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102 changes: 60 additions & 42 deletions PyNvCodec/TC/src/FFmpegDemuxer.cpp
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Expand Up @@ -236,67 +236,86 @@ void FFmpegDemuxer::Flush() {
avformat_flush(fmtc);
}

bool FFmpegDemuxer::Seek(SeekContext &seekCtx, uint8_t *&pVideo,
size_t &rVideoBytes, PacketData &pktData,
uint8_t **ppSEI, size_t *pSEIBytes) {
int64_t FFmpegDemuxer::TsFromTime(double ts_sec)
{
/* Internal timestamp representation is integer, so multiply to AV_TIME_BASE
* and switch to fixed point precision arithmetics; */
auto const ts_tbu = lround(ts_sec * AV_TIME_BASE);

// Rescale the timestamp to value represented in stream base units;
AVRational factor;
factor.num = 1;
factor.den = AV_TIME_BASE;
return av_rescale_q(ts_tbu, factor, fmtc->streams[videoStream]->time_base);
}

int64_t FFmpegDemuxer::TsFromFrameNumber(int64_t frame_num)
{
auto const ts_sec = (double)frame_num / GetFramerate();
return TsFromTime(ts_sec);
}

bool FFmpegDemuxer::Seek(SeekContext& seekCtx, uint8_t*& pVideo,
size_t& rVideoBytes, PacketData& pktData,
uint8_t** ppSEI, size_t* pSEIBytes)
{
/* !!! IMPORTANT !!!
* Across this function packet decode timestamp (DTS) values are used to
* compare given timestamp against. This is done for reason. DTS values shall
* monotonically increase during the course of decoding unlike PTS velues
* which may be affected by frame reordering due to B frames presence.
*/

if (!is_seekable) {
cerr << "Seek isn't supported for this input." << endl;
return false;
}

// Convert timestamp in time units to timestamp in stream base units;
auto ts_from_time = [&](double ts_sec) {
auto const ts_tbu = (int64_t)(ts_sec * AV_TIME_BASE);
AVRational factor;
factor.num = 1;
factor.den = AV_TIME_BASE;
return av_rescale_q(ts_tbu, factor, fmtc->streams[videoStream]->time_base);
};

// Convert frame number to timestamp;
auto ts_from_num = [&](int64_t frame_num) {
auto const ts_sec = (double)seekCtx.seek_frame / GetFramerate();
return ts_from_time(ts_sec);
};
if (IsVFR() && (BY_NUMBER == seekCtx.crit)) {
cerr << "Can't seek by frame number in VFR sequences. Seek by timestamp "
"instead."
<< endl;
return false;
}

// Seek for single frame;
auto seek_frame = [&](SeekContext const &seek_ctx, int flags) {
auto seek_frame = [&](SeekContext const& seek_ctx, int flags) {
bool seek_backward = false;
int64_t timestamp = 0;
int ret = 0;

switch (seek_ctx.crit) {
case BY_NUMBER:
seek_backward =
last_packet_data.dts > seek_ctx.seek_frame * pktDst.duration;
ret = av_seek_frame(fmtc, GetVideoStreamIndex(),
ts_from_num(seek_ctx.seek_frame),
timestamp = TsFromFrameNumber(seek_ctx.seek_frame);
seek_backward = last_packet_data.dts > timestamp;
ret = av_seek_frame(fmtc, GetVideoStreamIndex(), timestamp,
seek_backward ? AVSEEK_FLAG_BACKWARD | flags : flags);
if (ret < 0)
throw runtime_error("Error seeking for frame: " + AvErrorToString(ret));
break;
case BY_TIMESTAMP:
seek_backward =
last_packet_data.dts > seek_ctx.seek_frame;
ret = av_seek_frame(fmtc, GetVideoStreamIndex(),
ts_from_time(seek_ctx.seek_frame),
timestamp = TsFromTime(seek_ctx.seek_frame);
seek_backward = last_packet_data.dts > timestamp;
ret = av_seek_frame(fmtc, GetVideoStreamIndex(), timestamp,
seek_backward ? AVSEEK_FLAG_BACKWARD | flags : flags);
break;
default:
throw runtime_error("Invalid seek mode");
}
return;

if (ret < 0) {
throw runtime_error("Error seeking for frame: " + AvErrorToString(ret));
}
};

// Check if frame satisfies seek conditions;
auto is_seek_done = [&](PacketData &pkt_data, SeekContext const &seek_ctx) {
auto is_seek_done = [&](PacketData& pkt_data, SeekContext const& seek_ctx) {
int64_t target_ts = 0;

switch (seek_ctx.crit) {
case BY_NUMBER:
target_ts = ts_from_num(seek_ctx.seek_frame);
target_ts = TsFromFrameNumber(seek_ctx.seek_frame);
break;
case BY_TIMESTAMP:
target_ts = ts_from_time(seek_ctx.seek_frame);
target_ts = TsFromTime(seek_ctx.seek_frame);
break;
default:
throw runtime_error("Invalid seek criteria");
Expand All @@ -312,17 +331,18 @@ bool FFmpegDemuxer::Seek(SeekContext &seekCtx, uint8_t *&pVideo,
};
};

// This will seek for exact frame number;
// Note that decoder may not be able to decode such frame;
auto seek_for_exact_frame = [&](PacketData &pkt_data,
SeekContext &seek_ctx) {
/* This will seek for exact frame number;
* Note that decoder may not be able to decode such frame; */
auto seek_for_exact_frame = [&](PacketData& pkt_data, SeekContext& seek_ctx) {
// Repetititive seek until seek condition is satisfied;
SeekContext tmp_ctx(seek_ctx.seek_frame);
seek_frame(tmp_ctx, AVSEEK_FLAG_ANY);

int condition = 0;
do {
Demux(pVideo, rVideoBytes, pkt_data, ppSEI, pSEIBytes);
if (!Demux(pVideo, rVideoBytes, pkt_data, ppSEI, pSEIBytes)) {
break;
}
condition = is_seek_done(pkt_data, seek_ctx);

// We've gone too far and need to seek backwards;
Expand All @@ -341,11 +361,9 @@ bool FFmpegDemuxer::Seek(SeekContext &seekCtx, uint8_t *&pVideo,
};

// Seek for closest key frame in the past;
auto seek_for_prev_key_frame = [&](PacketData &pkt_data,
SeekContext &seek_ctx) {
// Repetititive seek until seek condition is satisfied;
auto tmp_ctx = seek_ctx;
seek_frame(tmp_ctx, AVSEEK_FLAG_BACKWARD);
auto seek_for_prev_key_frame = [&](PacketData& pkt_data,
SeekContext& seek_ctx) {
seek_frame(seek_ctx, AVSEEK_FLAG_BACKWARD);

Demux(pVideo, rVideoBytes, pkt_data, ppSEI, pSEIBytes);
seek_ctx.out_frame_pts = pkt_data.pts;
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15 changes: 13 additions & 2 deletions PyNvCodec/TC/src/NvDecoder.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -145,7 +145,7 @@ struct Dim {

struct NvDecoderImpl {
bool m_bReconfigExternal = false, m_bReconfigExtPPChange = false,
eos_set = false;
eos_set = false, decoder_recon = false;

unsigned int m_nWidth = 0U, m_nLumaHeight = 0U, m_nChromaHeight = 0U,
m_nNumChromaPlanes = 0U, m_nMaxWidth = 0U, m_nMaxHeight = 0U;
Expand Down Expand Up @@ -195,6 +195,7 @@ cudaVideoCodec NvDecoder::GetCodec() const { return p_impl->m_eCodec; }
int NvDecoder::HandleVideoSequence(CUVIDEOFORMAT* pVideoFormat) noexcept
{
try {
p_impl->decoder_recon = true;
CudaCtxPush ctxPush(p_impl->m_cuContext);
CudaStrSync strSync(p_impl->m_cuvidStream);

Expand Down Expand Up @@ -753,9 +754,19 @@ bool NvDecoder::DecodeLockSurface(Buffer const* encFrame,
*/
auto ret = false;

// Prepare black packet data in case no frames are decoded yet;
// Prepare blank packet data in case no frames are decoded yet;
memset(&decCtx.out_pdata, 0, sizeof(decCtx.out_pdata));

/* In case decoder was reconfigured by cuvidParseVideoData() call made above,
* some previously decoded frames could have been pushed to decoded frames
* queue. Need to clean them up; */
if (p_impl->decoder_recon) {
p_impl->decoder_recon = false;
while (!p_impl->m_DecFramesCtxQueue.empty()) {
p_impl->m_DecFramesCtxQueue.pop();
}
}

if (!p_impl->m_DecFramesCtxQueue.empty()) {
decCtx = p_impl->m_DecFramesCtxQueue.front();
p_impl->m_DecFramesCtxQueue.pop();
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10 changes: 10 additions & 0 deletions PyNvCodec/TC/src/Tasks.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -875,6 +875,16 @@ DemuxFrame::~DemuxFrame() { delete pImpl; }

void DemuxFrame::Flush() { pImpl->demuxer->Flush(); }

int64_t DemuxFrame::TsFromTime(double ts_sec)
{
return pImpl->demuxer->TsFromTime(ts_sec);
}

int64_t DemuxFrame::TsFromFrameNumber(int64_t frame_num)
{
return pImpl->demuxer->TsFromFrameNumber(frame_num);
}

TaskExecStatus DemuxFrame::Run()
{
NvtxMark tick(GetName());
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32 changes: 9 additions & 23 deletions PyNvCodec/src/PyNvDecoder.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -469,8 +469,7 @@ bool PyNvDecoder::DecodeSurface(DecodeContext& ctx)
Surface* p_surf = nullptr;
do {
try {
auto const no_eos = true;
p_surf = getDecodedSurfaceFromPacket(nullptr, nullptr, no_eos);
p_surf = getDecodedSurfaceFromPacket(nullptr, nullptr);
} catch (decoder_error& dec_exc) {
dec_error = true;
cerr << dec_exc.what() << endl;
Expand Down Expand Up @@ -521,8 +520,7 @@ bool PyNvDecoder::DecodeSurface(DecodeContext& ctx)
ctx.SetOutPacketData(pktDataBuf->GetDataAs<PacketData>());
}

auto is_seek_done = [&](DecodeContext const& ctx, double time_base,
double duration, double pts) {
auto is_seek_done = [&](DecodeContext const& ctx, int64_t pts) {
auto seek_ctx = ctx.GetSeekContext();
if (!seek_ctx)
throw runtime_error("No seek context.");
Expand All @@ -531,13 +529,11 @@ bool PyNvDecoder::DecodeSurface(DecodeContext& ctx)

switch (seek_ctx->crit) {
case BY_NUMBER:
seek_pts = seek_ctx->seek_frame * duration;
seek_pts = upDemuxer->TsFromFrameNumber(seek_ctx->seek_frame);
break;

case BY_TIMESTAMP:
seek_pts = seek_ctx->seek_frame / time_base;
seek_pts = upDemuxer->TsFromTime(seek_ctx->seek_frame);
break;

default:
throw runtime_error("Invalid seek criteria.");
break;
Expand All @@ -549,22 +545,12 @@ bool PyNvDecoder::DecodeSurface(DecodeContext& ctx)
/* Check if seek is done. */
if (!use_seek) {
loop_end = true;
} else {
MuxingParams params;
upDemuxer->GetParams(params);

if (pktDataBuf) {
auto out_pkt_data = pktDataBuf->GetDataAs<PacketData>();
if (AV_NOPTS_VALUE == out_pkt_data->pts) {
throw runtime_error(
"Decoded frame doesn't have valid PTS, can't seek.");
}
if (!out_pkt_data->duration) {
throw runtime_error("Decoded frames has zero duration, can't seek.");
}
loop_end = is_seek_done(ctx, params.videoContext.timeBase,
out_pkt_data->duration, out_pkt_data->pts);
} else if (pktDataBuf) {
auto out_pkt_data = pktDataBuf->GetDataAs<PacketData>();
if (AV_NOPTS_VALUE == out_pkt_data->pts) {
throw runtime_error("Decoded frame doesn't have PTS, can't seek.");
}
loop_end = is_seek_done(ctx, out_pkt_data->pts);
}

if (dmx_error) {
Expand Down
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